Merging the FBX files
You can merge the FBX files that contain referenced objects in two ways: merge append and merge replace. For example, consider that File_B.fbx is being merged into File_A.fbx as shown in the following figure.
The results of a merge append are shown in the following figure.
The results of a merge replace are shown in the following figure. The REF1 and REF2 from File_B.fbx replace the REF1 and REF2 in File_A.fbx. The reference edits from File_B.fbx is also merged.
Important: Do not use the same namespace when merging files with referenced objects that contain constraint connections to the scene objects. The merge process considers the namespace. If the same namespace is used, the constraint connections are broken because the merge process renames the namespace to avoid duplicate names.