Loading the flight plan from the Flight Tablet into the FMC in the PMDG 737 in Flight Simulator
On initial inspection I missed that this was possible, because the user interface is somewhat misleading. It turns out you CAN pull the flight plan directly from simbrief to the tablet, and then straight into the FMC in the PMDG Boeing 737 fleet with the new Universal Flight Tablet. It will only pull the route through (not the SID or STAR), but that might be useful if you have a long route to program.
It's worth noting that you can also pull the performance data, and the wind through as well through similar means. It's a little clunky - but it works.