I needed a ladder in my game and researched a lot and found none easy to do. I always try to look for simple ways using the resources of Construct 2 to solve my problems. The alternatives that I thought were difficult and required some calculations of the ladder height in relation to the dimensions of the 'char_soul'.
Studying some solutions I created this simple soluction to available to anyone interested.
Just use 'platform' behavior for your 'char_soul'. Use 'solid' for floor behavior and 'jump thru' for stairs. The best: no need to change any of the default control setup.
The variable to climb the ladder is global, because for some reason it did not work as the instance variable.
If you do not want your 'char_soul' to move left or right, set 'NO' to Default Control Platform.
To position the 'char_soul' in the middle of the ladder, use the "Soul > Stairs.X + Stairs.Width / 2" line for the character of your game, not in their 'char_soul'.
Hope you enjoy.