Hi, thank you for your review!
I still work on it from time to time when I find bugs, but it has pretty much reached the point where I am happy enough with its features, using it daily.

a way to minimise open folders -> I could definitely add something like this, but I need to figure out how: either a sort of taskbar, or simply a "minimize button" (or on double-click?) that would collapse the window into its title-bar, or reduce it into a small icon (like on NeXTSTEP environments).

a way to open all bookmarks in the same or a new window -> I tried to do that previously, but it was a bit difficult to make it work correctly, because each window would need its own history, navigation buttons, path, and then I'd need a way to right-click or Ctrl-click to open in a new window... and I didn't find how to do it with the Extension API. I'll explore this a bit more, hopefully without making the code too complicated.

a way to reorder the bookmarks -> that's an other feature that I thought about but abandoned, I'll re-read the documentation to see how I could do it.