Thanks for the warm welcome and taking the time to reply.
I had a look at the submesh example you posted and see the benefits submeshes buy you in terms of multi-materials. Would it be possible to query a submesh and apply a transformation to it, such as changing it’s position or scaling it along an axis?
Having looked at a subMesh in more detail it appears to be an abstract holder for a limited section of a mesh rather than a mesh in its own right. This means the answer to your question is no, unfortunately.
To me it looks like to create a ‘Vertex Group’ as you need, according to your description, there are two ways to go.
Manipulate the vertex data within a section of the mesh, probably using matrices.
Build a new mesh for each section of the vertex data you want as a vertex group, parent these new meshes to a root and then position and scale the new meshes individually.
Where is the mesh you want to divide into groups coming from? Are you creating it directly with Babylon.js or are you importing it?