custom interchangeをブループリントで作っていますが

[UE_FlavienP]

1. You should see the custom attribute on any static mesh that is referencing your original material.
   

   

2. for your Interchange Blueprint Pipeline, use the Interchange Editor Blueprint pipeline. this is available since 5.5. Load Asset is editor only function.
   

   

3. You will get the set material if you use the Interchange Editor Blueprint pipeline cf. 2