That's specifically the feature that I asked Victron to implement -- measure the DC loads via a separate shunt. Right now, you can't get that page to use a separate shunt. You can, of course, separately monitor the second shunt on your own.
The furnace fans do use a lot of power, yes. I don't use that, though - I use the mini-split heat pump. I just need to take the time to measure individual circuits. I already figured out that my jacks, even in standby mode, use a low of power, so those have their own switch to completely cut them off. There are probably other similar ghost loads I can turn off.