Re: Export Button Is Grayed Out.

"Export as  new files" is the short command name in the organizer to write to disk new files from selected files (not layers), 'New' generally means something different than simple duplicates or unchanged copies: for instance resized, converted to new format or custom renamed. 'Export' in the organizer also implies that the newly created files are made available externally to any other organizing or editing software without being included in the catalog.

The 'Save as' editor command also combines the ability to create copies while converting and/or renaming.

Since you are wanting to create new files from layers, it would help to understand what is the point of needing new files for different layers. We could perhaps suggest other solutions than the good one provided by @Peru Bob .

Delete all but one layer and then Save as the file under a new name.

Undo the deletions and then do the same for the other layers.