Make scroll bars wider Firefox

[LarryB1607]

Trying to use this procedure I found online:
https://forums.linuxmint.com/viewtopic.php?t=286908

I know this is from a Linux Mint forum, but not sure why it would not work as the base is still Ubuntu 18.04.

Here are my terminal errors:
Welcome to Linux Lite 4.8 larrypc

Tuesday 23 June 2020, 13:24:10
Memory Usage: 1116/7967MB (14.01%)
Disk Usage: 8/34GB (28%)
Support - https://www.freecinema2022.gq/forums/ (Right click, Open Link)

 larrypc  ~  xed .config/gtk-3.0/gtk.css

Command 'xed' not found, but there are 16 similar ones.

 larrypc  ~  locate .config/gtk-3.0/gtk.css
 larrypc  ~  touch .config/gtk-3.0/gtk.css
 larrypc  ~  xed .config/gtk-3.0/gtk.css

Command 'xed' not found, but there are 16 similar ones.

 larrypc  ~  touch .config/gtk-3.0/gtk.cs
 larrypc  ~  .config/gtk-3.0/gtk.css
bash: .config/gtk-3.0/gtk.css: Permission denied
 larrypc  ~  locate .config/gtk-3.0/gtk.css
 larrypc  ~  

I usually make appearance changes in userchrome.css, but that does not apparently work with this version of Firefox.

Any other suggestions appreciated.