Do you know if there is a geodatabase diagrammer for arcgis pro?
To my knowledge, no there is no ArcGIS Pro equivalent of Geodatabase Diagrammer. I did find an old version (ArcGIS Desktop 10.5) located here that may be of some assistance.
We're moving to ArcPro later this year, but the loss of Diagrammer will be a big problem. Any updates on this?
Not to my knowledge.