I posted here looking for an answer
https://www.reddit.com/r/LibreWolf/comments/16gc8ja/adapting_custom_butt...
It's working fine for my Firefox non-portableapps install, I'm tried to set it up for my portableapps LIbrewolf install. I "think" I did everything else right, but I don't know where to put the contents of these installation folder scripts. In Firefox, they go directly into the install directory.
https://raw.githubusercontent.com/xiaoxiaoflood/firefox-scripts/master/u...