If so, this is a pretty drastic design flaw in my opinion. I am the GIS Admin at my org and I have migrated to Pro. I have ten other GIS users that have yet to make that transition to ArcGIS Pro, however. I am attempting to recreate my old attribute assistant workflows from ArcMap in Pro. I was able to do so but immediately noticed that when I opened an old map from ArcMap, that the data source was broken. When I attempted to point it to the feature class, nothing happened. The little red exclamation point remained. Is this intentional or am I seriously being forced to use ArcMap until I can convince 10 people who have been using ArcMap for 10+ years to upgrade? They are extremely unlikely to upgrade, so it seems like my hands are tied unless I just force them to make the upgrade. I would prefer not to force anyone to do anything. I've been making the case for users to switch and believe they will do so when they see fit. Not to mention transitioning and training 10 new users of ArcGIS Pro would be a pretty substantial time sink for me.
