That simple? No configuring of FMP or VC batch files?
The frequency is being tuned via a discriminator tapped radio and the voice going out by rtl-sdr.
No. For a conventional (non-trunked) single-frequency DMR signal, you feed DSD+ with *either* a tapped radio or an rtl-sdr dongle, not both.
Sounds like you want to feed DSD+ from your tapped scanner, which you will tune to some digital transmissions. The tap's audio is being fed into a line or mic input on your PC? DSD+ has to have its input directed to that audio source. To do that, you need to have the <number> part of the -i<number> parameter on the DSD+ command line pointing to that audio source.
I'd suggest copying your VC.bat file to a new file - Discriminator.bat; just use Notepad to create the new file as well as to copy the text from VC.bat
Then just edit the new batch file; you don't need -rc so get rid of that, and change the -i number to the right number for your mic/line in input. You can get better performance out of DSD+ if you limit its decoding to the type of signal you're monitoring, i.e. add -fr to the command line for DMR-only decoding, but then DSD+ won't recognize any other digital signals, like NXDN, P25 - so your call on that.
Any time you want to feed DSD+ from your scanner, just run your Discriminator.bat file. No other programs are involved - no FMP, Unitrunker, etc. required.