The 3D Viewer will handle assemblies if the data is coming from Teamcenter and you use the extra 3D Viewer for Teamcenter module. If you have got PLMXML data, then it probably comes from Teamcenter
Hi Jeremy,
As I informed you in the support ticket, and to make is this information available for the community, this functionality is currently unsupported in Mendix.
Consequently, a custom development extension would need to be created to implement it.
Today, there are some flows in the Teamcenter Connector only.