Cool! Seems to be mostly working, the thumbnails do feel a bit squished though, I think this may be because whatever logic you have to generate the thumbnails is trimming the transparent excess but the preview always expects it to be in a 1:1 aspect ratio.
Either the thumbnails should be generated in a 1:1 aspect ratio, or the TextureRect/Sprite2D (whatever underlying node you're using to display them) should not stretch it to 1:1 at all times)
Also, 2 large chunks of assets got their icon generated quite quickly but now every time I hit refresh it just does the one asset before the last generated thumbnail
If my assets are like this, 50 with no thumbnail, 50 with a thumbnail (in that order), then the next refresh it will be 49 with no thumbnail and 51 with a thumbnail (again in that exact order, instead I would expect it to start from the first asset and work its way forward in chunks)
