The arrangement of certain icons in a browser game we like always bugged us, so we re-arranged them in Inspect Element. The problem is that every time we reload the page, the icons revert back to their original places. This is a problem because the page needs to be reloaded to get to certain parts of the game, never mind all the times it gets accidentally reloaded when the power runs out.
We tried looking up a solution, but the only guide we found only told us how to do one specific thing. We've never made an add-on before.
Yes, your description sounds like a text-book use for Tampermonkey.
With Tampermonkey, you do not need to write an extension ("add-on"). Tampermonkey is the browser extension, and you add it like any other browser add-on. Here is the link for the Tampermonkey extension for Chrome. (Tampermonkey is not just for Google Chrome - you can get a Tampermonkey extension for all popular browsers, via their usual extension/add-on pages).
With Tampermonkey, you can create little bits of javascript and CSS that Tampermonkey will inject onto the page just before it displays that page to you. You can completely reformat the page - you can even add new things onto the page that were not there originally (buttons, images, pop-ups...)
There are also many pre-written Tampermonkey scripts that you can install into your instance of Tampermonkey. Here is one example of a repository of a few Tampermonkey scripts.
Here is another StackOverflow answer that will get you started using Tampermonkey.