User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:92.0) Gecko/20100101 Firefox/92.0

Steps to reproduce:

open a submenu of a bookmark folder on the bookmark toolbar

Actual results:

the submenu is misaligned (see screenshot)

(btw the items of new UI is much higher than old ones, making some of my bookmark folder need to scroll.)

Expected results:

They should align nicely.

Oh, it doesn't vertically aligned with the toolbar item well, either.

The Bugbug bot thinks this bug should belong to the 'Firefox::Bookmarks & History' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Can you test the issue while in Safe Mode? You can find helpful info here : https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode .
Also a fresh new profile could help. You can find more about creating a new profile here : https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems#w_6-create-a-new-firefox-profile .
If possible, you can test this issue on the nightly build as well. Download the build from : https://www.mozilla.org/en-US/firefox/nightly/all/ .

Hi, it's already nightly + new profile. I just tried safe mode and it's the same.

Emma, this appears to be a regression from bug 1703051. Are you able to take a look?

https://hg.mozilla.org/mozilla-central/rev/5f5fbfefc86e

Go ahead and nominate this for Beta approval when you get a chance.

Comment on attachment 9237840 [details]
Bug 1720835: adjust top margin for menupopups in placestooolbar

Beta/Release Uplift Approval Request

• User impact if declined: Menupopus are misaligned on Linux
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: On Linux:

1. Open the "other bookmarks" folder in the bookmarks toolbar
2. Open a nested folder within "other bookmarks"
3. Notice the menupopups are aligned

• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): No string changes
• String changes made/needed: n/a

Comment on attachment 9237840 [details]
Bug 1720835: adjust top margin for menupopups in placestooolbar

Approved for 92.0b9.

https://hg.mozilla.org/releases/mozilla-beta/rev/6fcd235c9420

Reproduced the issue on Firefox beta 92.0b8 (20210824191834) build on Ubuntu 18.04.
Verified fixed on Firefox beta 92.0b9 (20210825224239) and Firefox Nightly 93.0a1 (2021-08-26) (20210826031555) on Ubuntu 18.04.