[Affected versions]:

• Firefox Release 99.0.1 (64-bit)
• Firefox Nightly 101.0a1 (2022-04-23) (64-bit)

[Affected Platforms]:

• macOS 10.15.7
• Windows 10 x64

[Steps to reproduce]:

1. Launch Firefox, and access "about preferences".
2. Scroll down to the ”Language“ area.
3. Click on the "Set Alternatives..." Button and then pop up the "Firefox Language Settings" window.
4. Add muliptle languages to the window until 6 languages are added.
5. Observe the "OK", "Cancel" and "Help" Button.

[Expected result]:

• A scroll bar appears next to added languages, allowing the user to scroll through the languages. And "OK", "Cancel" and "Help" Buttons display normally.

[Actual result]:

• These Buttons ("OK", "Cancel" and "Help") move down and cannot be displayed completely. The window needs to be dragged to display the full Buttons.