I have currently changed the original file, but it gets replaced with every Composer update.
Specifically, it concerns this code FancyBox
I have already entered the path to my custom.css in extend.php, which works perfectly.
return [
(new Extend\Frontend('forum'))
->css(__DIR__.'/assets/extensions/smart-button-community/smart-button-community.css'),
];
Now I would like to add the part or the changed PHP file if possible. 😉