[Bug]: Private Window icon takes up way too much space with vertical tabs

[Hate9]

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 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

When in a private window with vertical tabs enabled, the "private window" icon is horizontally next to the tab-list, taking up a bunch of UI space for no apparent reason.

Reproduction Steps

1. Enable vertical tabs
2. Restart
3. Open a private window

Expected Behavior

The icon should be below the tabs, not next to them.

Actual Behavior

The icon is beside the tabs, which looks weird and makes the tab text less readable.

Screenshots

Browser Version

11.14.1

Operating System

Arch Linux

Additional Context

No response