[Bug] First Child Inconsistent w/ Firefox Tabs Causing Conflicting Tab Navigation

[megamorphg]

Steps to reproduce

• Open Firefox in a new profile
• Install Sidebery
• Set "Place new tab opened from another tab" to "First Child"
• Open 1000 tabs and unload
• In one tab open many tabs

Actual behavior

Firefox tab menu spawns the tabs in Last Child order by default it seems and when setting to First Child, sometimes (under heavy load perhaps), Sidebery is not properly moving the tabs as First Child.
This then causes navigating through tabs (by Ctrl+PgUp/PgDown) to be in the order of Firefox's tab menu instead of the First child order.

For example notice how the tabs are in a different order:

I prefer to open tabs in First Child order so that I can open many tabs and then go to the bottom-most tab (the oldest tab) and start reading upwards.

Edit: on further testing this behaviour is happening w/ Last Child as well if rapidly opening tabs. It seems to be a speed issue. I do have 5k+ tabs (most of the unloaded) in different windows so I wonder if this is related.

• After a restart it seems to fix for a bit.
• It seems to especially happen with tabs opened from pinned tabs.
• It does very strange things like jumping to different tabs many tabs across sometimes (even though the next tab was nowhere near in either Sidebery nor the native tab bar).

Expected behavior, possible causes and additional notes

Firefox tab bar and Sidebery child tabs appear in same order and strange tab jumping doesn't happen.

System

Windows 11

Firefox version

153

Sidebery version

5.6.0.1

Logs

[sidebar:9] tabs.fg.groups.updateGroupOrItsChild: 922 7112 500 3 chunk-E5GSAC76.js:4:9308
[sidebar:9] tabs.fg.groups.updateGroupOrItsChild: 922 7113 500 3 chunk-E5GSAC76.js:4:9308