UserChrome.js stand-alone snippet loader by AveYo

featured snippets (Addressbar = Open input as URL on Enter - press Tab to Search instead & OneClickSearch)
also available for other popular js loaders in the chrome/JS folder

ELI5 request: sorry, age restricted

1. in firefox, open about:support and take note of Application Binary

   • for example: C:\Program Files\Mozilla Firefox\firefox.exe

2. open a Command Prompt (Admin) or Windows PowerShell (Admin) window

   • press Win+X on windows 10
   • write notepad and press Enter
   • the following steps are done in the Notepad window that just opened

3. File - New

   • copy-paste the UserChrome.js content

4. File - Save As C:\Program Files\Mozilla Firefox\UserChrome.js

   • browse in the dialog to the path noted at step 1
   • write at File name: UserChrome.js
   • select Save as type: All Files
   • select Encoding: ANSI or UTF-8

5. File - New

   • copy-paste the defaults/pref/enable-UserChrome.js content

6. File - Save As C:\Program Files\Mozilla Firefox\defaults\pref\enable-UserChrome.js

   • browse in the dialog to the path noted at step 1, and further to defaults / pref subfolder
   • write at File name: enable-UserChrome.js
   • select Save as type: All Files
   • select Encoding: ANSI or UTF-8

steps for linux and macOS are similar, using Terminal and sudo nano/gedit/TextEdit

For MacOS the file paths are /Applications/Firefox.app/Contents/Resources/UserChrome.js
and /Applications/Firefox.app/Contents/Resources/defaults/pref/enable-UserChrome.js ref