That can be done without home switches or anything.

Fasten your sacrificial block onto the bed, position the tool where you want the hole by guesswork / eyesight / ougie board etc Zero all the axis at this point in Mach by clicking the Zero x, Zero Y etc buttons at the side of the DRO's

Drill your hole with the cutter, move away, tap it, fit screw, press Goto Zero button, under the DRo's and it will return to where you drilled your hole every time.