I'm trying to create a relationship field, and I'd like to lock it down to a custom type. However, I'm getting a bunch of errors and the UI won't let me select a custom type.
This issue has been discussed in this thread, please notice that there is already an issue that has been created for this and our dev team is working on the fix.
There is also a workaround mentioned in that thread that is basically to add the constraint manually in the Custom Type JsonEditor
Please let us know if you have any other questions,