How to "turn off" an Action

I have the “add a new row to another table using values from this row” Action inserted in a deck view of applicants. The action is a star in the bottom right corner of every deck/applicant in the view and the idea is for the information associated with THAT applicant to make it over to a new table called “Watchlist” once their star is tapped. However, Im realizing that I do not want a user to add an applicant to their watchlist more than once. So how do I “turn off” the action but only after its been used and only for the applicant for whom it was already used?

You need to set a proper expression for the If this condition is true property of the action so that the action will be displayed or not.