Merging .scriv files

Hello. I was wandering: is there a way to merge 2 scrivener files, other than drag drop? I would need everything, including keywords and custom meta data to be merged between the 2 files… is it possible?

Yes, you can import one complete Scrivener project into another one:
File -> Import -> Scrivener Project.

See Section 11.1.7 in the manual for details of where all the pieces of the imported project go.