Standard roles cannot be edited, therefore, to set a preferred custom form for these roles, it must be set as preferred directly on the custom form. However, the form cannot be restricted there, so the users can still change the form they use when entering transactions or records. Restrictions to a form must be defined from the Manage Roles page and require the standard roles to be customized.
Navigate to Customization > Forms > Entry Forms / Transaction Forms
Preferred form: Click Edit/Customize
Click Roles
Desired role:
Preferred: Enter Checkmark
Click Save