Hi @hmccabe 

you can read its description if you expand the group and click on it:

basically you can remap the default metadata placeholder references for the document default metadata.

if you are populating your metadata consistently, then it has very little effect as it is only something authors will see. it can be useful in organizations where there are metadata already in place with defined placeholders, so they can be matched by clicklearn.

in practical use, i personally don’t think it is worth the effort to remap it. And it may cause confusion among authors.

It is a legacy feature that has been brought forward from classic when you could not define your own custom metadata which you can in attain now.