I'm converting between 2 issue types using "move". The message (screenshot below) indicates there is a way to update fields in those issues or to select Retain to keep the values. I don't see a way to select Retain.
Also, I don't understand why it is only showing one field (a field we don't use and haven't customized or differentiated between the issue types) rather than the many other fields that ARE different between these two types.

Thanks