The modeling tools are mainly TSX and RSX plugin addons that make using the software more functional and flexible. Some are 3rd party products useful in creating 3D artwork with Truespace and other modeling software.
A user on another forum uploaded a PDF Manual for Truespace 6.5 that Truespace and Gamespace modelers will find useful in the absence of an Insruction Manual. You can download it @ Design Devil TS 6.5 PDF Manual. There are some differences but both 3d modelers are basically the same operation wise. PS: I continue to use GSL quite a lot under Windows ME, so it still has some usefulness afterall.