This is for Dynamics and Model Driven Power Apps in General. Dataverse supports many-to-many relationships, but there is no easy native way to handle these relationships on forms. I suggest adding a multi-select combobox or some other option to allow developers to more easily take advantage of many-to-many relationships.

In my solution, I needed a way for users to "tag" data. The tag table and main table needed a many:many relationship. I had to make a manual join table so I could access it (as I could not access the hidden table created when making a many:many relationship), then embed a canvas app, which has come with it's own set of problems.