Material Slot in Editor Utility Widget UI

Hi there,
I am creating a widget for my substance material workflow. The creation of the slots and materials from picked textures works as intended but I would like to create a “Master Material” slot in the interface so the texture are created with a material instance based on that master material. Something like this:

I already did that from inside the editor graph but is “hard coded” in a sense…

I wanted to make these master materials swappable in a way that I can basically drag & drop them inside the slot and create a new instance based on that slot.
Is there any way I can achieve this?
Any help would be greatly appreciated.

You ever managed to solve how to do this? I’m making a Dialogue tool for my writers and designers and I want them to be able to change the Sound Wave assets from the tool, but I haven’t found any documentation on it :confused: