Items you will need:
6 buttons
4 zones
4 teleporters
2 barriers
(Disclaimer: This cannot work for more than 2 floors!)
First make your elevator. Make 2 elevators. One on one floor and another on other floor. Now in the door way add a barrier.
Wire a button (the button on the outside of the elevator) to the barrier: button pressed → deactivate barrier. Make that button say “Open Elevator.” Now add another button except it is inside the elevator. Make it say “Open Elevator.” Now wire that button to the barrier: Button pressed → deactivate barrier. It should look like this currently 
Now add a button on the other side of the inside of the elevator. (Do this for both elevators)Name it Descend.
(Do this for the first elevator NOT the second one (not yet anyways)):
Now the tricky part. Ok. So wire the descend button to a teleporter. Button pressed → Teleport player to target. Have the teleporter target as “lower.” DO NOT HAVE ANYTHING IN THE GROUP SECTION. Ok now do this for the second elevator but the teleporter for the second one have the target as “Upper.”
Have that? Good. It should look like this currently⬇️ (For both elevators)
Now add a zone in the elevator (Do this for both elevators) Wire it to the barrier/door: Player Enters Zone → Activate Barrier
Now add a zone under the barrier (outside of the elevator) and wire it to the barrier: Player Enters Zone → Activate Barrier. It should look like this for both elevators currently⬇️
Now add 1 teleporter in the middle of the elevator for each elevator. Name the first teleporter in the first elevator “Upper” for the Group section. For the second elevator the name the second teleporter Group Section “Lower”
Now it should look like this when done (for both elevators)
Thanks for reading this tutorial and if you liked it drop a like! If you have any questions or comments, comment them below!
Sir Quillius Inkpot