How to write a (simple) Firefox add-on as simply as possible, without deep learning?

Question

JavaScript

The ability to change page content on the fly is required.
Of course, there are all sorts of Greasemonkeys, custom buttons and something else, so far I have only superficially studied it all, but I can’t find the time and there are serious reasons to study it.
Therefore, I decided to ask the experienced - those who have already created extensions, what can they advise in order to "quickly roll" the extension - a button that allows, when pressed, or in some cases, immediately when the page is loaded, embed a div into the page code block and be able to influence the page with its js code as well as read the necessary elements of the page. In general, I know that this is possible, but I would like to know the shortest paths to this, for example, ready-made sources for such add-ons, add-on templates, with a description of how to compile these sources without installing additional tools.
No, I'm not lazy, I just grew out of the age when you want to study everything on your own, the brain no longer wants to accept it.

Answer 1

For myself, I hastily wrote a simple extension for FireFox, having looked at their guide on creating extensions . I needed to install nodejs and jpm .
I do not claim that this is the easiest way possible, although I achieved the expected result quickly, and from my point of view, easily.

Answer 2

In 2016, it was possible like this https://capweb.ru/kak-sozdat-sobstvennoe-dopolneni...
Now it rolls with prof. version of Mozilla. for normal permission setting is blocked, most likely you need to find a way to sign the extension, for example, like this
https://habr.com/post/355144/