MPCs inside Material Instances cannot be swapped

Summary

When you add a material parameter collection to a material, then make a material instance of it, there is a slot inside the material instance to swap the MPC, but it doesnt work (doesnt show all MPCs in the project, and the create button in it does nothing).

Please select what you are reporting on:

Unreal Editor for Fortnite

What Type of Bug are you experiencing?

UI/Tools

Steps to Reproduce

Create a material and add a material parameter collection in it
Duplicate the material parameter collection
Create a material instance and add the second parameter collection in it

Expected Result

Second MPC can be slotted inside the MI

Observed Result

Second MPC doesnt show when trying to set the MPC inside the material instance. Pressing the create new button doesnt create it either.

Platform(s)

pc