Sad to say that Tree Tabs is less buggy than Piro's "Tree Style Tab."

Although a few navigation bugs make Tree Tabs awkward to use,

1) When the option "Append child tabs to the top" is enabled, Ctrl+Tab|Ctrl+Shift+Tab navigation browses tabs as if "Append child tabs to the bottom" was enabled -- in reverse order.
c.f. Open two tabs from parent, Ctrl+Tab once, the bottom (2nd tab is activated). Ctrl+Tab again, the focus moves UPWARDS (not down) to the first child tab.Ctrl+Tab a third time, focus leaves the tree downwards to the next parent tab.
Expected Behaviour, Ctrl+Tab: 1st child activated, then second child, then leaving tree to next parent tab.

2) When navigating tabs via Ctrl+Tab|Ctrl+Shift+Tab, collapsed trees are expanded and traversed, instead of skipping to the next parent tab.

- Existing unloaded tabs are ignored when saving Tree Tabs session.

- No option to change Tree Tabs font family (perhaps can be rectified with CSS like pre-Firefox 57).