How to save/export only selected parts

Good afternoon,

Houw can I save only selected parts from various sub-assemblies from the main assembly? And eventually export them to an STL document. I can't export the whole document, because it is too large.

I tried to look for the create sub-assembly option, but I don't think I can use this on parts belonging to different sub-assemblies. Thanks,

SolidworksImport export