List of steps to reproduce (step by step, including full links if applicable):

• Create a new user defined type, e.g. Positive Integer with a single key of type String
• (note that that type does not get displayed, there's a separate bug for that, T299192 )
• Try creating an instance of that type

What happens?:

• The field for the key is not displayed.

What should have happened instead?:

• I should get a field to enter the string value

Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc.:
As of January 19, 2022