I have the same issue on Cubase 14 on MacOs with Serato Sample. I created this thread here.
It is working with Cubase 13 on the same machine though.
The drag and drop functionality is really strange. For instance I can even drag and drop audio from the sequencer timeline to Cableguys Snapback plugin like you can do with Steinberg Plugins like Padshop, but not on any other third party plugin.