I'm sure I'm not the first one to ask - how about multi-line tabs? A single line gets overcrowded quite soon.
We are religiously opposed to multi-line tab bars. They are a user interface crime. 
I look at it in a slightly different way - as a programmer, I often do things that I'd never ever do for myself, but if my paying customer insists, I'll sometimes close my eyes and do it anyway.
Just an idea - this might be a half-hidden option in advanced page of settings.
We do lots of those things (else Opus wouldn't have thousands of options in Preferences), but we have to draw a line somewhere. Multi-line tabs have so many usability issues, as the UI Hall Of Shame points out.
There may be better ways to deal with that many folders/tabs than letting them spread on to a second line of tabs.
This article is at least 15 years old not that up-to-date in interface design. Also it is focused to options dialogs, not document/viewer layout which more relates to Dopus use-case when browsing files.
Anyway, I myself don't have the need for so many open tabs, but I do understand the need for multi-line tabs. Visual Studio also doesn't support them, but many people (including) myself bought a little plugin called TabsStudio, which allows exactly that. And it really helps organizing and saves time.
If it's too complex for you to implement it, then I would understand. But you can't say that you are "religiously opposed" to multiline tabs if it is useful for quicker navigation (dropdown definitively isn't, especialy since you need two clicks instead of one - not to mention that you can't close those in dropdown since they don't have X button).
The issues the article raises have not changed in 15 years, and I don't see multi-line tabs being popular in e.g. web browsers where it is incredibly common to have lots of tabs open, or in anything really, and for good reason.
There are usually better ways to deal with the problem than multi-line tabs (or the overflow menu, which is not the solution I was advocating). Which I'd recommend depends a lot on why so many tabs end up being opened in the first place, so I haven't recommended any specific alternative.
Nobody has ever complained about not being able to close tabs via the overflow menu before, AFAIK.
This is obviously one of those holy wars (so this is my last message on the subject as I don't want to argue endlessly).
I don't know from which survey you've pulled that info - TabMixPlus Firefox extension that re-introduces multiline tabs has 1.2 millions of users. Try to google and see how many people claim they won't use Chrome because there is no such extension there.
Anyhow, DOpus is your software, you can clearly do whatever you want with it. But I hardly see any reason why not to have multiline tabs (such as different number of rows with dual listers - something that wouldn't bother me), certainly not any 'good' ones.
To ggenter: the implementation is actually trivial as tabs control can return its current dimensions, which is most probably already used.
[quote="leo"]The issues the article raises have not changed in 15 years, and I don't see multi-line tabs being popular in e.g. web browsers where it is incredibly common to have lots of tabs open, or in anything really, and for good reason.
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Nobody has ever complained about not being able to close tabs via the overflow menu before, AFAIK.[/quote]
Browser is somehow different, it can display much more tabs in caption, and it usualy has web page icon which can help you find your tab even when it's text is almost gone (due to many opened tabs).
In file system 99% of the folders have same icon so that can't be used to distinguish folder tabs, only names.
Like I said, 99% of the time I don't use so many tabs, but if I did, I would also like to have multi line tabs. It gives you much better overview of open tabs and you can close those that are not needed anymore with only one click.
For example, on my desktop computer I fill my tab space (in dual view) with only 5 tabs (I display full folder name). Now, since I don't plan to buy bigger monitor anytime soon, I could get one or two more tabs by using "Reduce tab sizes to fit available space" option, but I don't like to trim folder names. I could also use some condensed font for folder tabs, but that look bad. 5 tabs isn't that much. And also using dropdown for more tabs is just awkward. You can't know how many tabs you have open until you click on the dropdown, and even then, you must click one of them to close it. Too much clicking, and too much hidden information from user.
If it is easy for you to implement it, an option to use it would certainly be great. Different users, different needs. And like you said, you already have tons of options 
Fast and easy use should be important. Nobody wants to use file manager more than it's required to.
I've been wanting multi-line tabs since I started using Dopus a few years ago. I also use TabMixPlus in Firefox and Multi-line Tabs is MUCH easier to work with than a single line of tabs.
I have a fair amount of screen real estate so I use a dual lister but I only use Dopus on half the screen. I end up getting 2-6 tabs before running out of space on either side even with short folder names. Then adding more tabs causes them to reduce in size until I can't see what they are. I usually only use 4 or five tabs but sometimes I need to open a bunch and I really want to be able to single-click on the tabs to make them active just like on Firefox with TabMixPlus.
There are some issues with multi-line tabs which TabMixPlus helps with. For example, I have all the tabs reduce to the same user-selectable size before the tabs go multi-line. Having all the tabs be the same size helps quite a bit because when closing tabs or opening them, everything moves left/right in a predictable fashion so it is much easier to visually remember where things are. Right now, Dopus doesn't have any controls for the tab sizes. They just reduce in size until only icons are shown. If multi-line is used, there also needs to be settings which force the tabs to shrink to a user selectable setting. Only when the line of user-selectable smallest size tabs is full does it open the next tab on a new line. Then I could actually keep the tabs much larger and still see some of the label on each tab. If I could have 3 tabs per line for example, I could have 9 tabs open on 3 lines, I would easily see enough of the folder names to identify them. It is much easier to switch between them too. To me this is obviously easier to work with than the current system of one line of tabs with a drop-down. Again, look at the extensive options that TabMixPlus has to control Tab Sizes. TabMixPlus is very well thought out with lots of settings.
The "hall of shame" example shows another bad implementation of multi-line tabs. it actually moves the rows around when you switch tabs. That's not necessary and mixes the locations of all the tabs. For multi-line to work, it is important all the tabs stay in place so one can visually remember the locations of the tabs. When a Tab is selected, it only needs to be highlighted. It shouldn't move like all those old silly Windows Settings boxes with multi-line tabs. Those are very confusing to use. I don't have problems like that when using TabMixPlus. Implementing multi-line correctly is important or it is useless! With TabMixPlus, having all the tabs reduced to the smallest size and then making them into basically a grid of same-size tabs helps a lot because no tabs move around when switching between them.
I agree that some people may find the multi-line tabs to not be to their liking but I would certainly use at least two lines of tabs quite often if I had the option available. It is definitely more efficient for me. I sometimes have 2-3 lines of Tabs in Firefox and it's a lot easier to navigate than with Internet Explorer where I need to click the right arrow 4 times for example and all the tabs are moving left/right. With multi-line, I always know a particular tab represents a particular location. That doesn't change unless I open/close a tab and even then, it is very predictable how the tabs are moved. Using a drop-down to select always repositions the tabs so the selected tab is visible and you never build a "memory map" of the tabs.
So please consider adding Multi-line Tabs at some point for the people who know they will use it. I suggest the developers extensively test out TabMixPlus on Firefox specifically with different options for Multi-line tabs. Who knows? You may even find out that with the right settings, it can help in some circumstances! Unfortunately, it seems clear that this is a fairly major feature that would be quite difficult to implement properly but I think it would be worth it at some point.
(But, for sure, no more than 1,199,999 of those users use multiline tabs).
Monitors used to be 4:3 or 16:10 aspect ratio. These days with extra-wide monitors being made at 16:9 aspect ratio (mainly for cost-savings since they share manufacturing with TV panels) - Vertical Tabs might be useful.
Possibly in single lister configurations. In dual, I don't think there's enough space for that...
While I think that classical 'jumping' tabs are a mistake, I could definitely find use for some kind of better implementation. Too often I end up with the same folder opened multiple times, because it is hidden somewhere in the overflow menu, where I don't bother to look.
Exactly, I can't see why there is a "religion" which hates multi-line tabs and likes dropdown overflow of single-line tabs
Like I said, main issue with this "design" is that it hides important navigation information from user, and Dopus is all about quick navigation.
All tabs should be equally accessible.
If you have so many tabs open you can't remember which tabs you have open, what is the point of the tabs at that stage?
I think the problem is in whatever is causing so many tabs to be open, forgotten, and never cleaned up. I'd prefer to look at ways to solve that (whether by using existing features or adding new ones) than ways to put a bandaid on the problem.
Making the UI show more and more tabs just encourages that mess to build up, and I can't imagine reading through three or four lines of folder tab labels to check if a tab is already open before clicking a folder to open a new one; that seems counterproductive.
The "findexisting" mode of opening a new tab can help, and doesn't require keeping track of which tabs are open.
Tab groups, multiple windows, layouts, styles and toolbar buttons/menus to open common folders (without dedicated folder tabs for them all the time) can also help in situations where tabs are building up. I think there are much better solutions than just throwing more tabs on the screen, if people think about why they're ending up with so many tabs in the first place. It seems very unusual to need to simultaneously work in so many folders that they don't fit on one line of tabs with the existing options (e.g. to shrink-to-fit the tabs if they overflow by a bit).
They can't. Even if the tab lines don't move to keep the selected one next to the file display (which breaks the visual metaphor, but whatever), as soon as you close a tab the rest all jumble around.
(But, for sure, no more than 1,199,999 of those users use multiline tabs).[/quote]
Make that 1,199,998 as I use TabMixPlus in Firefox and wouldn't touch that option with a barge pole. 
I know you won't take me seriously, but there's only a thin line between this and removing vertical scrollbar from listers and focusing to address the problem of why there are so many files in folder... 
That is ridiculous.
I agree. But, I see identical type of reasoning in both cases.
There are lot of folders with lots of files in. They exist already and people need to work in them.
On the other hand, you choose when to create folder tabs and there are probably better workflows than opening 30 of the things.
I can't see much constructive happening from either side of the debate in this thread (apart from the idea about allowing vertical tabs, which might make a good option for some people) so I'm going to do my best to ignore it now, as we'll probably just argue otherwise.
Actually, you can already do that: Put Go TABLIST=icons or similar on a vertical toolbar.