In my app I had a folder of images from which I was getting the names to use as keys to a Dictionary. I have now moved all images to an asset catalog and created groups for
You have two choices:
Don't Do That. Go right on using a folder of images.
Supply the keys in some other way. If you don't want to hard-code them into the code itself, you could make a text file. But of course you will have to keep that text file updated as you add / remove images.
You'll notice that I didn't say you could magically introspect the asset catalog. That's because you can't.