Reviving this as it’s still an issue with UE 5.3.2 version in 2024…
@Lovecraft_K , I saw that you provided a solution here: Delete old material, replace with material instance doesn't work - #2 by Lovecraft_K
However it’s currently not possible. UE gives an error/warning “The object to consolidate are not the same class”. Did they just drop this feature and not provided a better solution?
Nevertheless I found out a workaround with Property Matrix, I shared details here: Easy way to replace all references of a material? - #9 by filibis