Alright, an update to the 5th Generation Map Editing guide!
This one is all about the g3dcvtr.exe, I can tell you about some of the commands I haven't mentioned yet.
g3dcvtr.exe [name].imd -etex [output name].nsbtx
If you want to only export the model, type in this:
g3dcvtr.exe [name].imd -emdl [output name].nsbmd
If you want to export the model with the textures, type in this:
g3dcvtr.exe [name].imd -eboth [output name].nsbmd
For a list of other commands, be sure to put in "g3dcvtr.exe --help".
Note: If you're importing nsbmd models as maps or buildings, you must convert the .imd file to nsbmd without the textures by using the -emdl command, otherwise the game will freeze upon loading the model when imported.