Your comments

Yes, I made some tests and it seems that I'm wrong about this - for all purposes apart from the icon difference a Group seems to be equivalent to a named window. I thought before even named windows disappeared when you close them but maybe I was wrong. So this argument doesn't hold that much. Regardless, I'd rather use the TO tree to regroup tab clusters, rather than the Chrome toolbar. After all TO is supposed to visually replace the toolbar, according to Vladyslav's own workflow suggestions in the introduction videos (I think).
The classic use case is when one tries to sort out a window full of tabs into subgroups. Quite usually, clusters of about 5-10 tabs would be connected but they wouldn't be hierarchically related in a tree and can't be easily moved out except one by one. Sure, one could use Chrome itself to do this but:

1) With many tabs on the titlebar, it's next to impossible to know which tab is what, while this is readily obvious in TO

2) Moving them out in Chrome creates Windows and not Groups (personally I prefer Groups, as they are less prone to accidental closing and sometimes even Chrome can't bring recently closed windows back due to bugs, while TO doesn't save closed windows)

3) Don't know if TO is supported on Mac, but Chrome on Mac does not allow multiple tab selection (which is incredibly stupid, but that's another story)
Sounds awesome, crossing fingers :)
Thanks! I have tried leaving everything expanded but for some reason this really slows down operations on the TO window, not really sure why, seems like Chrome is struggling with this enormous DOM tree, which is weird.

I'm not familiar with the implementation but I'm not sure why would re-installing TO and then dragging the very same tree you had before into it, affect the RAM usage? What kind of info do you keep in the data files that would lead to accumulating RAM usage over time? I would think it's only a link and a session state (like, i don't know, tab history?). If the session state preservation is to blame, then the workaround you suggest is not really optimal, as it probably destroys the associated sessions?
I, too, would donate about this feature

Yes, I understand that it involves some heuristics and that there are edge-cases with possibly wrong re-association, if the Chromium improvement does not get implemented. The Save-Close-All button is indeed a workable solution but it has two negatives for me personally: (1) i forget about it sometimes, it's more effort than it should be; (2) once reopened, the last windows are not visually distinct in any way - they only have the (closed Aug 27, ...) label but for me they should stand out more (perhaps bolded or green).

This morning I opened a new windows and then closed it and I realized that if it were autosaved, I'd not be happy. So I agree with your assessment that maybe auto-save every window by default is not the best way to do it.

But how about differentiating between a single window close and a Chrome-wide "exit"? Does the API allow you to distinguish these two cases? If it does, you could auto-save all open windows on "chrome exit" but not auto-save generic windows on single close. You could even flip a flag and auto-restore those windows on Chrome startup if "startup with Chrome" option is checked for TO. This way, you would effectively replace the "continue where i left off" option and people would be happy.

Another question - when Chrome crashes, is it 100% certain that TO would preserve all open windows? The uncertainty about this is another reason for me to stick to "continue where i left off".

For what it's worth, I strongly double this opinion - it is exactly what TO needs to become a truly great plugin. As of now, I just can't find a workable solution of preserving my session when i need to reset Chrome for whatever reason. This leads me to keep "continue where i left off" checked which on the other hand causes ten thousand duplicates on crashes. Vladyslav, I understand that if solved, the issue in Chromium would be the perfect solution for you, but it's only got 7 stars by now and it's probably not really high on the priorities list. Meanwhile, in 0.4.48 you implemented auto-save for windows but opted to keep root level default windows out of it. If you extend this auto-save to all kinds of windows, it would automatically serve as a session restore, especially if you can set a flag on isWindowClosing and bring those windows back to life on startup. I understand your concern that preserving all windows by default creates a mess, but as heavy users of your plugin I think we can absolutely assure you that this behavior is very much desired in order to allow TO to fully replace all other session software in Chrome. And lastly but most importantly, thank you for all the great work on this!