I'm looking to have a custom fields with a pre-defined pick list (or other values) that my Marketo users needs to use so they cannot randomly add what ever they want into this field. The idea is it control what goes into the fields to fit the business need
E.g.
Field: Role
Type. String
Pick list:
If they can edit the Form, they can certainly edit this.
You need to train them to use the Template and/or stick to the guidelines.