You don’t necessarily need a custom plugin for that, just remove the gravity from the main rigidbody and add the gravity force yourself on every physics step. Of course the rules how to apply it depends on many things on your gameplay.
If you just base the rules for gravity direction by ground normal, you’d simply add force to your rigidbody with value that is -980 * mass_of_the_rigidbody * ground_normal where 980 is the gravity value on unreal.