1/ I don't made the srcattribute type itself editable in the displaytab. I think this is not something that normally will change after first creation. If people have good reasoning to allow other types on other displaytabs, I can add a generic mechanism to allow editable comboxes in displaytabs
2/ I added private column to displaytab (http://www.gramps-project.org/bugs/view.php?id=6780
), but this is not editable. As privacy is an important thing we don't want people changing by accidently clicking somewhere, I did not do this.
3/Don't suggest to make complicated fields editable in displaytabs. So not eg Name of a person, as that is a compound field.