This is a misunderstanding.

There are Percussion Layouts, and there are Percussion MIDI Maps.

Percussion Layouts are saved inside the Finale document.

You can save a document’s Percussion Layouts as a Library that you can load into other Finale documents.

Percussion MIDI Maps are saved in a special file, in a special folder.

From that folder, the Percussion MIDI Maps are available to all your Finale documents.

The Percussion MIDI Maps are not saved inside the Finale document, and you can not save a library with Percussion MIDI Maps.

When you send a Finale document to someone else, you must also send the file with the Percussion MIDI Maps used in the Finale document.

Path to the folder with the Percussion MIDI Maps (for Mac Finale):

(hard drive)/Library/Application Support/MakeMusic/Finale 26/MIDI Device Annotation