Hi fdjveiga,
You’re going to run into some problems with additional collision components when you use Character class, as class is designed specifically for vertically-oriented player representation and Capsule is meant to be primary collision detection for world. It sounds like you’re making a different type of character, one that includes a board. You’re probably going to need to create a mesh that includes both and has various animations for movements, hit reactions, falling off board, etc. Then you’ll need to create a custom Pawn class rather than a Character class.
If you’d still like to do it way you have it in your pictures above, you can create a Pawn class Blueprint, set up a Capsule as your Root, have your character’s Skeletal Mesh below that, and board below that. With that setup, world should detect collision on your board. You’ll need to set up your own movement controls in that case, though.
Hope that helps!