The addon which has the functionality that, for whatever reason, Firefox doesn't have built-in.
Everything is working as expected except that when adding about:home to the list, it ignores it and everything else that comes after. Other than that it is working great.

Gets the job done, sadly it's a bit clunky to reorder the tabs in a way that I want them to open up. So in my case it's better to just have my urls inside a bookmark folder then open that folder as my homepage in native firefox settings.