Files for left side added in the appropriate folder, use the ones you need accordingly.

Update: Now resizable!

-Allows the sidebar to open on a floating window and close when clicked outside

-Toggle on or off

Installation:

• Install the following https://github.com/xiaoxiaoflood/firefox-scripts
  • on step 3 follow: utils → I'm only interested in scripts
• Go to settings => manage profiles => find the default profile => root directory and click open folder.
• Paste zip contents there
• Navigate to about:support and click "Clear startup cache…" to force Firefox to load userChromeJS on the next startup.