Since 5.14, it is always possible to use drag&drop to move remote files to external applications, while copy is always the default operation.
I'll consider that. Also to duplicate files, you can hold down 'Ctrl' key while dragging.
one more thing... it is also useful to have a drag-and-drop menu to copy (duplicate) or move a remote file to the remote server (from file panel to tree panel, in Explore-like mode). Now you can only move a file with drag-and-drop, Duplicate is only accesible with right-click/Duplicate (but this needs you to enter manually the path).
When drag-and-drop a remote file to an Explorer folder with right mouse button, it would be nice to have a Move option. You can do this with right-click on the file and then Move-To, but it wuold be easier with drag-and-drop.