As I know, Quick3D supports maximum 8 morph targets and remains will be ignored. But Custom QQuick3DGeometry can only support one morph target.
Some code is out of sync in qssgmesh_p.h and qquick3dgeometry.h when handle QSSGMesh::MeshInternal and QSSGMesh::RuntimeMeshData.
Finally, any plan to support more morph targets? 8 morph targets is not enough in practice.