What others have stated will work to show the issue.
But...
The NSS path is starter relay terminal to the NSS, when the NSS is in the correct position it grounds out.
With the DVM in continuity mode (beeps when the leads are connected) and connected to the wire that goes to the NSS and battery negative, when you run the trans lever through its positions the meter should beep in 2 places, N and P.
If it doesn't beep or beeps in the wrong position you know you have an issue with the switch or the rooster comb