[Bug]: Show sidebar button removal not persistent.

[thoth-amon]

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.
• [ ] 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.
• [ ] 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

Show sidebars button reappears in the same place every browser restart despite being removed,

Reproduction Steps

1. Open Browser
2. Remove "show sidebars" button which is next to the back button.
3. Close and Restart Browser.

Expected Behavior

Removing the show sidebars button is persistent.

Actual Behavior

Removing the show sidebars button is not persistent.

Screenshots

Browser Version

11.14.1

Operating System

OpenSuse Tumbleweed.

Additional Context

No response