Update to Firefox Developer Edition (October 2024) results in the following issues

[erre213]

Toolbar icons disappear, leaving only the extensions icon. Even the '+' icon, which is used to add tabs, disappears, as well as those that are usually to the right of the address bar.

I have already restored the toolbar defaults;
I have entered diagnostic mode;
I have deleted prefs.js and xulstore.json in Mozilla\Firefox\Profiles\;
I have deleted all cookies and history, etc.;
I have deleted the Mozilla folder entirely and reinstalled Firefox;

Nothing works. In some cases, the icons come back, but after closing and reopening Firefox, the problem repeats, only the extensions icon appears, and nothing else.

[weirdsciencex]

I can confirm, I'm experiencing the same issues, any attempts to rectify only works until a browser restart and then the UI is broken once again. 

[pew_pew]

I can confirm the same issues.

[PartyVan]

Same here its broken did try some steps like OP mentions

[pencilEar]

I am having the same issues. I originally thought it might something corrupted so I uninstalled using revo uninstaller and then reinstalled. The first time I opened the browser it looked fine, but since then it has been looked weird. refresh button is gone. forward and backward button is to the right. extensions button is to the left. If I change the toolbar configuration it just goes right back to this weirdness next time I open the browser. And all my bookmarks are gone. 

[BennyStils]

Logged in here just to report that the same thing is happening to me: customized toolbar settings reset every time I restart FF.

[reis]

same...

[CBIweb]

I can also confirm these issues.  In addition to the above, the entire bookmarks bar is gone and cannot be restored through the usual method.

The only way everything can be restored (in my experience) is with Customize Toolbar > Restore Defaults, but it only lasts for that session. I need to repeat that workaround every time I launch FF Developer.

I had hoped the latest update (132.0b2) was a fix, but it was not.

Running a fully updated Linux Kubuntu 24.04.1.

[CFreak12]

Same issue. Tried restarting the browser and computer and whatever fix I try it just reverts back to the weird broken topbar layout.