Error when clicking to see field properties when editing a form

I had an error a while back when working on customizing a form. I'm documenting the resolution to remind me an in case it helps anyone else.

The scenario is:

  • In a solution or the default solution, navigate to any entity
  • Open any form for the entity
  • In the form, double-click any field to change its properties

The following error appears

After a discussion with Microsoft support, the issue was that the System Customizer role did not have read privilege to Knowledge Search Model (prvReadKnowledgeSearchModel privilege)

Knowledge Search Model is on the Service Management tab.

Having selected read, editing the form worked as expected.