For the component, or entire design, edit the 3d body model. You can select either the bounding box, or the actual object made by just the lines, of any single layer, and have this define the 3d body. (The body itself can exist on another dedicated mech layer too.) So you can select just silk lines (not text) or just your assembly layer lines, etc. and if you don't always want to see the hatched lines when assembly layer is enable you can define a different layer to be for the 3d body that is left not visible in 2d mode. It will show up as a box in 3d mode to the height specified by the part, you get to pick color and opacity in the 3d body dialog.
A bit simpler and quicker than doing an extruded body model or STEP model.