Latest beta as always - 12.7.1.6593 
And indeed I meant just rereading the folder instead of monitoring it all the time while it isn't "on top".
Also as I mentioned earlier last time this happened there was only a single lister with 10 tabs on one side and 15 on the other so none of that 60+ stuff.
Also the weirdest thing is that I don't remember experiencing this before 12.6.9. Could be my memory. Could be windows' fault too.
We've implemented an experimental tab hibernation feature that you'll be able to switch on in the next beta. Once that's out, please give it a try and see if it helps out.
(At least initially, it'll only be for normal folders, not for things like collections.)
Using the new beta and it does seem to handle notifications nicely.
On the exact same day I installed it however - the slowdown happened again and at my wits end, I found this article.
Namely:
Ever since the so-called Fall Creators Update of Windows 10 (version 1709), Adobe Lightroom Classic CC has been suffering from what I believe to be the GDI GetPixel() bug
The symptom is that UI performance degrades gradually as Windows remains up, and only a reboot of Windows restores correct performance. Switching modes and tools (in Programs) results in very slow screen repaint after a few days of Windows uptime.
For anyone having this issue (probably everyone on Windows 10), this update seems to fix it:
-Dave
After manually installing the mentioned KB4058258 as winupdate refused to offer it to me by itself - so far all is good.
I'm positive this same bug was the one affecting dopus as like I mentioned before - the toolbars were gradually painted, lister redrawing was slow and erratic, focusing - unfocusing, and even filtering preferences made the results appear sequentially with visible lag between them and not instantly like on a fresh restart.
As it turns out the problem was on a lot larger scale than DOpus and I feel bad for making conclusions.
Fall creators update really did a number on us - until this update - hopefully.
To check if you have the update installed:
Interesting. My PC auto-installed that two days ago, and while I didn't have any issues in Opus, it appears to have fixed a problem I had in another app where its toolbar took about 30 seconds to draw.
It probably depended on how you have your toolbar set to look (e.g. background images).
Chalk it up to yet another Windows 10 bug in the end. At least Microsoft fixed this one.
Thanks for updating the thread!
Never thought I had images on them until now - I noticed the toolbars using Standard toolbar image was checked. Looks like that is the default for new toolbars - or at least was at some point in time. Turned them off and they look exactly the same with or without it 
In my case I noticed exteremely long startup times (10+ seconds) of a Video Splitter app which this update fixed so here's hoping for a long uptime 
In dopus' case it wasn't the startup - at first it runs flawlessly and gradually gets worse with longer system up-time so most people might never notice any slowdown at all.
They probably weren't using a background image if it didn't look like it. Standard toolbar image refers to one of the image slots under Preferences / Display / Images, but if no image is defined then it doesn't mean much. It lets you define the image in one place and get it on all your toolbars without having to edit each one individually.
I guess we can only speculate about what triggered the Windows bug and why some people saw it at different times. For me, one app did it all the time on one PC, and sometimes on another. Perhaps it's triggered by an interaction between apps.
I'm glad Microsoft have fixed it, whatever it was.