I was surprised, when I just took a swing at altering the "manifest.json" file (cynwoody's FRPFE extension), and that worked.
Then, I made some adjustments to the buttons and appearance in the https://freerepublic.com/perl/post webpage (re cynwoody's FRPFE extension), and that worked: I resized the "Your Reply" window, removed some buttons, and changed the URL address for the "Help" button, to:
HTML Editor https://htmltable.com/
Overall, thank you for asking/suggesting re javascript and extensions. The extension helps.