[Bug]: Vertical Tabs Issue

[FlameQuests]

Pre-Submission Checklist

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

Bug Summary

With vertical tabs, the indicator for a tab being in a container (coloured line) does not show when the container tab is on the top.

Screen.Recording.2024-12-23.154837.mp4

Reproduction Steps

1. Enable vertical tabs
2. Clear all tabs
3. Open up a tab in a container

Expected Behavior

A coloured line should show on top of the tab which is in a container

Actual Behavior

A coloured line does not show on top of the tab which is in a container

Screenshots

Screen.Recording.2024-12-23.154837.mp4

Browser Version

A coloured line should show on top of the tab which is in a container

Operating System

Windows 11

Additional Context

No response