Bookmark menu shows up in wrong place, and its entries' context menu has weird layout problem

Preliminary Checks

• I have read and understood the important section above.
• I have searched existing issues and avoided creating duplicates.
• I am not filing an enhancement request.
• I have checked that this issue cannot be reproduced on Mozilla Firefox.
• I have checked that this issue can be reproduced once I removed all my Mods and Custom CSS.

What happened?

When clicking on the bookmark menu button, the menu doesn't show immediately under the button, but in the middle of the screen.

Also right clicking on any of the entries will show a weird context menu where texts are cut off because the width is not enough.

Expected behavior

Bookmark menu shows up right under its menu button

Actual behavior

Bookmark menu shows up in the middle of the screen

Steps to reproduce

1. Add the Bookmark menu button to the toolbar
2. Click on the bookmark menu button
3. Right click on any of the bookmark entries

Screenshots and videos

No response

Version

1.15.5b

What platform are you seeing the problem on?

Linux (Flatpak)

What component is this issue related to?

Bookmarks

Relevant log output if applicable