Incorporate QGIS mesh editing tools
QGIS 3.22 introduced basic mesh editing features, which have since been refined.
They do however not support all features of the 2DM format; crucially they do not support element materials, or node strings.
One workaround is a mesh conversion feature that restores these lost features in edited meshes using an un-edited copy, which could be implemented as a processing algorithm. Ideally this could be integrated into QGIS proper, as was done with multi-materials for QGIS 3.16.