It’s not much about third party support, it’s about how it is triggered. At the very least, discord works. Since I have disabled notification for almost all of my apps except a few, I cannot tell too much. But, the “drag while float” design has a very high fail chance that even if I want to do it, I will more than likely expand the notification instead of dragging it as full windows. In short, I think the design is cool but needs some serious rework for better use.
This one is unrelated but wiggle mode should be removed entirely to avoid confusion and support haptic touch better. Just use context menu to trigger it and include a section in settings app to reorder apps and such.