Heirarchy not consistently persistent

Great work on the latest update. Many of my gripes are gone. This one persists...

Although I can't give you exact numbers at all, given how infrequently I shut all the way down, I would say that maybe 1/4th of the time, on unloading/reloading the browser (and sidewise), my heirarchy of sites/tabs is maintained. Another 1/4 of the time, it works partially (some sites/tabs get flattened out, others remain where they should be), and maybe 1/2 the time, the entire list gets flattened out into a list with no levels at all.

Looking forward to seeing this fixed.

THanks again for the great extension.

- m