Lasso/polygonal select of mesh boundary faces

Hi! I import 2d meshes into salome (surfaces ambedded in 3d), and need to mark different irregular subdomains on the boundary. The meshes are very irregular, and there is no underlying “constructed geometry” to make subdomain marking/tagging easy. It would therefore be very nice to have a “lasso select” or “closed polygonal select” similar to what Meshlab has for mesh boundary facets. It becomes very time consuming to do a rectangular selection, and then to edit it by adding/removing facets on at a time, expecially when the mesh is very fine.

Best regards,
Torquil Sørensen