I own a 2016 Outback. When the vehicle is moving an address destination cannot be entered (for safety reasons) But I have seen GPS units which will let the passenger enter the address. Does the SUBARU have this option, and if not, why not? The system could easily sense whether there is a passenger in the car-- in fact it does sense that fr purposes of airbag control.

This is unfortunately pretty common in an OEM GPS, though it is disappearing from more modern cars. One option I've used on other brands is to set up a toggle switch on the VSS (speed sensor) wire, toggle to open, program in your address, then toggle back. This tricks the GPS into thinking you're stationary, and allows you to program while the VSS signal is lost. Unfortunately you can't simply remove the VSS signal into the GPS, as it's used when going through tunnels, etc.