Generally speaking, you are taking your chances when any station where one or more metro lines and/or the RER intersect. Transfers may require walking long hallways and lot of stairs. Getting out of multi-line stations generally requires plenty of stairs.

As mentioned, there may be escalators, but those are often out of order.

More and more stations have had elevators installed. But, to determine which one, you have to use the RATP interactive map, click on each station, then click on the Information icon to see if there's an elevator.