Well in a new profile i can not reproduce because sometime along the way some tabs got that " --" at the end of the title that came from god knows where, surely didn't came from the website.
Although i managed to upload a striped sessionstore with only a "New Tab" that is broken in the original post above, you can download and test for yourself, as long as that tab is open or more tabs that are open coming from that particular one the issue persists, and honestly i got no idea where the " --" in the title is coming from.
I'm sure you know the sessionstore goes in the profile folder with the proper name.
Although i managed to fix the problem, I went back to test it and indeed it gave an error:
TypeError: lazy.ContextualIdentityService.getPublicIdentityFromId(...) is undefined3 TabsList.sys.mjs:323:40
_createRow resource:///modules/TabsList.sys.mjs:323
_populate resource:///modules/TabsList.sys.mjs:110
_populate resource:///modules/TabsList.sys.mjs:275
handleEvent resource:///modules/TabsList.sys.mjs:254
dispatchCustomEvent resource:///modules/PanelMultiView.sys.mjs:189
dispatchCustomEvent resource:///modules/PanelMultiView.sys.mjs:1484
_blockersPromise resource:///modules/PanelMultiView.sys.mjs:223
The fix is in the edit above.
Although i managed to fix the problem, I went back to test it and it indeed gave an error:
TypeError: lazy.ContextualIdentityService.getPublicIdentityFromId(...) is undefined3 TabsList.sys.mjs:323:40 _createRow resource:///modules/TabsList.sys.mjs:323 _populate resource:///modules/TabsList.sys.mjs:110 _populate resource:///modules/TabsList.sys.mjs:275 handleEvent resource:///modules/TabsList.sys.mjs:254 dispatchCustomEvent resource:///modules/PanelMultiView.sys.mjs:189 dispatchCustomEvent resource:///modules/PanelMultiView.sys.mjs:1484 _blockersPromise resource:///modules/PanelMultiView.sys.mjs:223
I actually just fixed it, the problem came from tabs with a " --" at the end of the title, probably added from some addon. Please check the edit above for more info.
I also can't reproduce with a new profile.
I literary copied my profile from %appdata% and pasted it in Windows Sandbox %appdata% for testing.
First i removed the chrome folder, could be the userChrome.css, nothing.
Second i removed all the extensions but the problem persisted, then i started closing tabs and at around 147 tabs closed it fixes it.
It crossed my mind it could be some extension that did something to a particular tab or something that breaks the list but it doesn't seem coming from a specific tab.
This only started a couple of days ago, probably when Firefox updated, not sure.
It also messed up a bit the userChrome.css where i had custom separators a bit where i fixed with the line "padding-block: 0px !important;".
"List all tabs" button won't show any tabs
In the latest Firefox version(116.0.2 (64-bit)) the button "List all tabs" won't show any tabs unless I close like half of them, then it works again if I open new random tabs. Currently 246 open tabs.
Any other way to fix this? I don't really wanna close those tabs.
The way I know this is that I tested in a sandbox with the same profile to try to find the problem.
EDIT 14/Aug/2023: So I just found out the issue was some tabs that had a " --" at the end of the title probably caused by some addon made this issue happen. It probably isn't really a - but I don't know what character is that.
All you have to do is just copy the url, open a new tab, paste the url and go. Close the previous tab with " --" at the end. Just make sure you are not opening a new tab with CTRL+(clicking the + icon) from the "broken" tab with the " --".
Hope this helps someone else.