The typical workflow would be as follows:
- Export the current mesh to a file (e.g., shp)
- Create a new mesh for the additional part by using a superelement that a) has exactly the number of nodes as the existing mesh at the common border. Use Triangle with the option to not insert Steiner points at the outer boundary to obtain exactly this number of boundary nodes.
- Export the new mesh to a file.
- Import old and new mesh at once.
- Set all parameters again.
This is just a temporary workaround, providing some more flexibility than version 6.0. For 6.2, it is planned to support direct adding of new supermesh polygons to an existing model.