Also check this page:
https://help.sketchup.com/en/sketchup/classifying-objects
scroll to Creating an SKC file.
It is based on XML and the schema is .XSD, if you open the Model Info [menu] Window >Model Info > Classifications, select the classification and then choos export, you can save it on your desktop (It defaults to the %AppData% )
Rename the file (change from .skc to .zip) and then extract.
I use Xcode to edit, but any editor will work.
Yes, you can have multiple tags…
but it is a hassle to label in LayOut
This one has the NAHB costcodes embedded in the embedded SketchUp file(!):
Bouwbesluit.layout (390,5 KB)