It seems like when you drag and drop a file onto Shapr3D canvas it should trigger the import function. To me, that should be almost the same behaviour as when someone airdrops a file to the iPad while that app is running.
Drag and drop is still not working in
Version 3.57.0 (726). I can provide a sample XCode project with an AppDelegate that demonstrates how that would work. I assume that is 101 type stuff for you but happy to do it if it can help in some way.