Create a code for a court and hand it to whoever sits there. It lets them score matches on that court only.
Create a join code for the tournament and attach it to one court.
Give that code to the person scoring at that court.
They can score any match scheduled on that court, without you assigning each match to them.
A code attached to no court gives no scoring rights at all. Always choose the court.
The first person to score a point on a match takes that match, so two people cannot score it at once.
Open the tournament and go to the section for join codes.
Create a code and choose the court it is for.
Label it with the court or the person, so you know later who is holding it.

Give the code to the person scoring at that court.
Revoke the code when the day is over.
Leaving the court empty is not a way to give access to every court. It gives access to none. Choose a court.
Anyone holding the code can score on that court. Use one code per court, and revoke it after the tournament.
Assigning somebody to a single match overrides the court code for that match.
Codes made for a deleted court stop granting anything. Make new codes if you rebuild the court list.