trees destroyed by moving tabs: firefox "move tab to end" or other extensions

[zesty]

Steps to reproduce

• Open Firefox in a new profile
• Install Sidebery
• make a few trees
• send a tab in the first tree to the end using right click on ff tab (not sidebery tab) Move Tab -> Move to End
• observe tree structures after the move

(might need some tabs at zero level in between the trees or after them)

Actual behavior

for "move to end" (right) all the tabs to the right will be sucked up into the current tree at the same level as the moved tab, destroying all trees; there is no undo

Expected behavior

the tab pops out of the current tree and moves to the end, and lands at zero level (not in the tree at the end at the same level as the original tree)

System

Ubuntu 22.04

Firefox version

129.0.2 (64-bit)

Sidebery version

5.2.0

Logs

No response

[zesty]

In addition to the firefox move tab feature, it seems that other extensions that move tabs around will also trigger the misbehavior. See for example All Tabs Helper which gives you a list of all your tabs in tight columns for dragging around.

I think there might be a missing hook to monitor the movement of tabs / change of tab order outside of the extension and respond appropriately.

[zesty]

possibly related to #1781

[axelsimon]

I've seen this too when involuntarily setting off keyboard shortcut to move the tab: it starts scrolling down the list of tabs quickly and on its way, every time it hits a child tab in a tree, makes every tab after that a child of the tree, creating this sort of structure:

This clearly shouldn't be happening :)