Sooo, I think the most part of that script is some libraries. The intersting bits are at the end of the script. There might or might not be difficulties because your script runs at start of document and mine runs at end. I do hook into new items for infinity scroll, so I do not care to wait for any fancy stuff with lots of asyncs. You seem to do things by applying classes too and let the browser handle things.
And I think your concept is based on the item still being visible by changing opaqueness, so you can still display those svg icons. Might have time to look into it in a few days.
But I believe the really interesting part of your tool will be the collection viewer. Applying styles to cells is not all that difficult. I did that with user style addons a lot earlier, before making that thingy. You might find old threads about this. That thingy just gives a button to that functionality, so you do not need to manually edit a css file. It also applies the styles directly to the items, but that is just a technical detail ;-)