I have two CPTs, MainContent, and Templates. The MainContent CPT has a clonable fields group. In that group, the user picks a template from a select field. The select field shows the elements from the Templates CPT via callback:get_my_templates. That works fine.
My problem is, how can I prepopulate the other custom fields in the MainTemplate group with the values from the selected Template custom fields? Is there an option to define a dynamic default value in a custom field? I know I can define a static default. But I need the default taken from the Template CPT. Is there a filter or hook I could use?