Don't take it wrong, but I'm getting wary of services offering to store my data online for free, especially when I don't know how / if it intend to make money.
Looks good though, I might give it a try even with that issue.
Firefox loads under a minute with 510 tabs from various tab-groups. (I use a tab-group for each group and field of study and yes I use most tabs actually)
The search in the sidebar is so enormously useful, it helps me to find ANY bookmark made by hitting CTRL+b or middle-click (two-finger tap here). I heavily use tags, which is really making the search better, but I wish these tags could be automatically generated by an algorithm.
1. https://addons.mozilla.org/de/firefox/addon/flat-bookmarks-h... (this is what opens up a better sidebar)
2. https://addons.mozilla.org/de/firefox/addon/bookmark-rater/ (rating is really useful sometimes)
3. https://addons.mozilla.org/de/firefox/addon/enhanced-middle-... (I use that to open the sidebar)
4. https://addons.mozilla.org/de/firefox/addon/auto-sort-bookma... (autosort "heap, stack and memory" of bookmarks. I don't sort the the toolbar)
Optional:
i) https://addons.mozilla.org/de/firefox/addon/faviconreloader (In case you want icons for old bookmarks)
ii) https://addons.mozilla.org/de/firefox/addon/tabgroups-menu/ (helpful to quickly switch, rename and reorder tab-groups, because zooming-in-out sucks)
iii) https://addons.mozilla.org/de/firefox/addon/unloadtab/ (worried about loading >500 tabs at once? set it to load only tabs you clicked and unload tabs oder n)