ACMS
and 330 I've flown don't have push to level off buttons......
Have a look at DSC-22_30-70-80 P 1/4 and DSC-22_10-40-20 P 1/8. You'll note in the graphic on the latter page, next to the V/S knob it says "Push to level off". By convention we use the ALT pb although pushing the V/S knob would have exactly the same effect.