What you can do right now is:
- Select module #1
- Edit the triggers associated with it.
- Select module #2
- Now edit the triggers that use *that* module.
Changing back and forth between modules is perfectly legal and won't harm your project. The module selection merely controls the labels on the triggers and within the note selection drop downs.
For the SPD-XX units (and for all other unsupported modules or software), simply use "General MIDI". For some units (such as the SPD-XX) there really aren't any custom mappings to speak of and GM can be used. This is also why the default module setting is GM.