I’ll provide my solution, I’m not sure if it’s the solution of all solutions though. 
First you need to put a socket on lower extremity of your character.
platform blueprint has 2 components: a box trigger and Paper Sprite. I hit Alt+K in component viewer to switch to side view. trigger is just slightly larger than sprite.
Here is Event Graph of my blueprint!
If you want to do moving platforms, I used an Attach To node in construction script to attach trigger(connect to Target) to sprite(connect to In Parent) and I used keep relative offset.
If you want be super careful about memory usage, I suggest you make 2 versions of blueprint, 1 with Sprite and Trigger set to movable and another where they are both set to static.
For your convenience I’ve uploaded a TXT file with entire event graph. Don’t worry about trying to mimic what I did!
Hope helps you. 