I decided to start a new thread for this, so as to contain the conversion.
I spent the better part of 12 hours trying to figure out why my extension does not work within Firefox. I loaded it locally, and tested all day long. It really should work.
The extension (or addon as Mozilla refers to it) does not make use of any esoteric calls. Everything that I am using within the CSS and JS files seem to be reported as being supported by Firefox (especially for the latest version - currently 69.0).
Yet, I cannot get it to work. When I use some of the debugger features, it seems that it never goes into the meat of the JS file sections ... such as the functions, the document.body event listeners, etc.
I don't know why. I am not really a web developer, even a front end one. I simply know enough to be dangerous.
Basically what I am saying is that I have reached the end of my knowledge set, and I cannot get it to work. If there are true developers out there that would like to take a look at the code, and try to determine what is wrong, I am willing to share the 2 files (1 CSS, 1 JS). Reach out to me via PM, and we can then converse via e-mail.