How do I drag a folder/file structure into my project?

It seems that I can only import files and not folders. Is there any way I can drag a complete folder with its subdirectories and files into my project?

Or some other trick to do this? My tree structure is too big to recreate it by hand everytime I need to update the files.

I don't think it's possible without some manual editing of the project files.

Note, that on export the folder structure will be flattened - all files will be moved to the root folder. So if you need to preserve folders in exported game, you probably shouldn't import them into the project.