Hi @Anonymous
I assume by the label (Book and unbook), the User is booking for an event. So in the data source, you have information on whether the current user is booked for that event or not.
Boo1 visible property should be
IsEmpty(Filter(DataSource,condition))
For Example, Checking whether a logged-in User is booked for the event this vent or not
IsEmpty(Filter(IssueTracker,EmailId=User().Email && Event=ThisItem.Event))
Note: For better performance, App OnStart set the property to, Set(UserInfo, User()) so this variable will be used all over the application like UserInfo.Email
