You already can.
Select List Raids > then select the raid which has the intercepting unit you want to place on patrol > Select Recall > on the recall page select Patrol against the intercepting unit you wish to assign to patrol. The unit turns green and is on patrol.
Herr von Shagmeister - correct you are! I never tried that. But just using Recall does not offer this option, which would be a nice.
Thanks!