I'm struggling with an existing many-to-many relationship which has broken after upgrading 7.5 to 7.6. There is a custom field on the join table that, when included in the subpanel definition, prevents any rows from being returned.
The existing relationships and vardefs have lots of different properties, some of which may be redundant or legacy properties left over from 6.x.
The Sugar docs only cater for creating relationships via Studio, and Studio doesn't provide for extra fields on the join table.
Most of the information I've found via Google search is for 6.x.
I have no idea which properties are required, or what the properties do.
I could post my specific problem here, but it would be involved and difficult to explain.