My initial approach to this wouldn't be to plan a route using pathfinding behaviour, although I understand the agent's general movement from place to place could be pathfinding. I would do it by using the floor I am on to locate an elevator that goes to the floor I want, and if one isn't found then to the closest floor I want. Using your image as an example, this is what my approach would be :
Elevators are objects that have variable attached to determine what floors they go to, it could be a set of booleans, floor1=true, floor2=true etc or simply a variable for the highest floor it goes to i.e. floorMax=5 it goes to 5th floor. I will use the first example for now as the second could pose problems for going in reverse, or I guess you could add a floorMin var.
Anyway, so I am on floor 1, I look for an elevator that is floor1=true as a priority (it goes to floor 1), and also goes to floor 5 destination (floor5=true). In your image that elevator does not exist, so it then looks for the next floors down. I need an elevator that is floor1=true and floor4=true, not found. Floor1=true and floor3=true. Ok i found it, it's the elevator on the left.
Then I get to floor 3, I look for an elevator that is floor3=true and also floor5=true. Yes that exists it's the elevator on the right, I path to this elevator and take it to 5th floor.