Unable to edit labels under Administer Compensation Additional Compensation section

Summary:

We have a request for several edits on the Administer Compensation > Additional Compensation section. We want to limit the values in the Plan dropdown box to a select list of plan values (hiding several plans from the list). Also, depending on which plan is selected, additional fields appear. Our users would like to modify the labels on these fields however the properties are greyed out for update. How can we limit the values listed under "Plan" and edit the Commitment Date label to read "Completion Date" when the properties are greyed out when attempting this via Page Composer > Structure?