How to rewrite the draw order?

Hello all, ive never modified the engine before and I thought this would be a good little experiment. Basically my end goal is to make an oldschool RE/Silent hill inventory - IE Inventory items are drawn in 3D over the HUD. Currently the goto method for that is using Render targets and scene captures and I really dont like that method because its messy and engines have gotten away with simply drawing the models over the UI for the longest time.

Does anyone know where I should start looking to modify the draw order. Ideally my setup would include some kind of array of objects that I add to and then whereever the draw calls are made, I make a function at the very end that draws the array of objects over everything else including UI