There’s a difference in how references are saved for Classic maps and WP maps.
World Partitioned maps save the dependencies per actor instance, so you should be able to see in the reference viewer immediately which actor the reference came from:
[Image Removed]Classic maps, on the other hand, save dependencies during save time for the entire map, so Reference Viewer can’t tell which actor introduced the dependency. There are two ways to figure out how that dependency got set.
“Resolve Referencing Properties”. This loads the map and figures out which actor introduced the dependency. This feature was recently introduced (not sure exactly when) but you can right-click the referenced object (the material in your case) in the reference viewer and click “Resolve Referencing Properties.” This should show the actor name that’s referencing your material.
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If the reference viewer isn’t working for you (you have an older UE version or it shows an error, which I’ve seen happening) for showing the reference for a classic (non-WP) map, you can insert a breakpoint during map saving to see when and why the reference is serialized into the map. This is a bit more advanced, but I explain how here: Failed to load [filename] Referenced by [function] - #7 by Ari_Epic