Many ways to do it.
you can create sharepoint list with emails of team members. Then in App.OnStart set variable
Set(IsMember,!IsBlank(LookUp(LIstName, User().Email = EmailFromList)));
The above variable will be Boolean.
Then on the button set this in the display mode property:
If(IsMember,Disabled,Edit);
Button will be disabled if he is in the team and enabled if he is not in the team.
Another methods will be same you just need a specific list against you can check and set your variable.
You can use office365group connector if they are in specific group.
If they all have 1 manager. And no other member in the organization have that person as manager. Then you can use office 365 user connection to check logged in user's manager. and update the variable accordingly