The BBEdit text editor for
developers has a plug-in mechanism to teach it to do syntax coloring, code folding and
such for languages it doesn't already know about. These plug-ins can be installed in the
~/Library/Application Support/BBEdit/Language Modules, where the tilde
stands for your home folder.
My VRML+3DMF plug-in provides syntax coloring and code folding for the ASCII formats of two 3D object file formats, VRML and 3DMF.