Middle click folder to open in new folder tab

New to Opus and I have been looking through the FAQ's and tried setting Opus up to open a folder in a new tab with a mouse button middle double click but it does not work at all for me, also none of the pre-defined commands, such as 'Left double click + alt' does not do anything either and wondered if I needed to do something else to enable these?

It's usually helpful to say what you've actually tried rather than just a generic "it does not work". The command you want, in any event, is Go NEWTAB, and you would assign it to the All Folders file type.

The "it does not work" was not generic it was refering to trying to open a new tab with various combinations of mouse and keyboard buttons, I am sorry if this was not clear from the subject and content of my question. I don't know what else to add as 'it doesn't work' - I followed the instructions in the FAQ and have re-checked them several times but I can't get a new tab to open by double clicking the mouse middle button or any of the other pre-defined commands in the file types menu, such as 'Left double click + alt' do not do anything either.
In addition to 'Go NEWTAB' I think I have tried adding all the commands given in the FAQ to the middle-click option in the file types-all folders-edit-events menu.
Just to be clear, the FAQ I am refering to is: Middle click folder to open in new folder tab

Does your middle mouse button actually work? If you have a logitech mouse you normally need to assign it as a 'generic button' before it can be seen by applications as a true middle button.

I've updated the FAQ in question to include some extra notes/details that might be what you're running into:

[quote][ul][li]Note: This does not affect single-clicking items. Single-clicking with the middle button always toggles a file or folder's selection, like left-clicking with Ctrl held down, unless you are using Power Mode and have configured the button to do something else.[/li]
[li]Note: This does not affect virtual folders which Opus does not handle itself. Try in a generic directory like C:\ if it doesn't seem to work elsewhere.[/li]
[li]See Also: Always re-use a single window instead of opening new windows[/li]
[li]See Also: How to make Logitech Mid/Back/Forward buttons work in Opus[/li][/ul][/quote]

It's an HP 5 button mouse with software to assign actions for the buttons, I have it set as a standard mouse middle button and it works OK with programs like Opera browser where I use it to open new tabs and I have button 4 set to 'left double-click' and button 5 as 'page-down' and Opus recognises both these.
The only things I can find that open a new tab are 'Ctrl-T' or through the file menu.

Think I have found out where I am going wrong on this.
I have been trying various combinations of clicks & keys on folders in the tree window, which has not had any effect at all but I have just discovered that they do work on folders that are displayed in the right-hand window, is this how Opus works or should I be able to open folders in a new tab from the folder tree?

Correct, it doesn't affect the folder tree. (I've updated the FAQ to mention that as well.)