For a moment I thought you might be referring to the “GrayBox” stairs in Fortnite/GrayBox/Stairs, but it sounds like this is in the context of modeling mode.
The easiest fix would be to change your created meshes collision complexity to ‘Use Complex Collision as Simple’ - Modeling mode meshes used to be created with this setting, but that changed in 34.30. (In my opinion this was a bad change, If I’m going to create a shape I’m probably also going to want to collide with it… using complex collision (actual geometry of mesh) does have performance implications though.)
Yes, I am referring to the stairs in modeling mode. Thanks for the clarification. Not sure why one even would want to provide primitive shapes without collision, especially stairs. No big deal, I’ll make my own.