[Bug]: On Linux with close/minimise/maximise buttons on the left, placing the tab bar below the toolbar moves them to the right.

[c-massie]

Pre-Submission Checklist

• [x] I have checked the existing/closed issues to ensure this issue has not already been reported.
• [x] I am using the latest supported version of the browser.
• [x] I have tried disabling all browser extensions/add-ons to rule out interference from these.
• [x] I have tried clearing the browser cache and cookies.
• [x] I have checked with a new profile and the issue still occurs.
• [x] I have provided detailed step-by-step instructions on how to reproduce the issue.
• [x] I have included relevant screenshots or console outputs.
• [x] I have checked that this problem is not occurring in the latest version of Firefox ESR.
• [x] This issue is specific to this browser and does not occur in other browsers.

Bug Summary

Using the Firefox Photon · Lepton UI, on Floorp in Kubuntu (Ubuntu with KDE) with the close/minimise/maximise buttons on the left.

This may also apply to Gnome when the close/minimise/maximise buttons are on the left.

In the Settings > Design > Tab Bar, when selecting "Display Tab Bar underneath the Toolbar", the close/minimise/maximise buttons move from the left of the window to the right.

This also applies to "Display Tab Bar at the bottom of the window".

Reproduction Steps

1. Go to settings > design > Tab Bar.
2. Click "Display Tab Bar underneath the Toolbar" or "Display Tab Bar at the bottom of the window".
3. Observe.

Expected Behavior

For the close/minimise/maximise buttons to remain on the left-hand side.

Actual Behavior

The close/minimise/maximise buttons move to the right-hand side.

Screenshots

See video.

https://github.com/user-attachments/assets/c62054d8-4eba-4419-babd-d3a7b7c4b336

Browser Version

11.22.0 (64-bit)

Operating System

Kubuntu (Ubuntu with KDE)

Additional Context

No response