Yes, Monkey Tools does require that you connect Excel with the Monkey Tools add-in to the Power BI data model, so I guess that’s a nonstarter for you.
Without an external tool, the best I can think to do is to screenshot the summary Manage Relationships screen, and then the individual screens for each relationship to document cardinality, directionality and active/inactive, per the screenshots below.
A similar screenshot could be taken of the data model view to show the table/field structures.
The most difficult one would be extracting measures from the PBIX file. I can’t think of way to do that other than manual cut-and-paste to an external file, without using a separate tool.
Perhaps someone else on the forum has an idea on how to do that in an automated way natively within Power BI.
I hope this is at least somewhat helpful. Power BI has really limited documentation capabilities built in, which is why so many external tools exist to fill this gap.
- Brian