/macro Activate "powexec_name White Dwarf$$ next_tray$$ next_alt_tray"
$$macro on "powexec_toggleon Dark Nova$$goto_tray 9"
$$macro off "powexec_toggleoff Dark Nova$$powexec_toggleon Gravity Shield$$goto_tray 1"
this is what I use to switch my trays. I hit my "on" button and I change to Dark Nova and my bottom tray changes to number 9. Then if I want to change back I hit my "off" button and I turn human, my tray changes back to 1 and I activate a shield because I'm usually taking damage when I switch.
I think your biggest problem is you need the goto_tray # and goto_tray_alt # instead of just tray and alt tray. I cant test it to make sure but I think thats it. Also you might make the marco name smaller. I'm not sure how many characters you can use tho. You should have something like
$$macro Act "powexec_toggleon White Dwarf$$goto_tray 9$$goto_tray_alt 8"