I don't remember if Trim Step can be changed on a per flight mode basis, but I know it can be changed per control function..

3 position switches can be used for almost anything controlled by a switch. Flaps for example.. Up being Flaps Up, Middle being Takeoff Flaps, and Down being Land Flaps. You could also use them to control flight modes.. Can you give me an idea of what you want to do? I'm not really understanding what you're asking I think.