Think about this for a moment ...
The transfer case is bolted to the back of the transmission, so, to get the transfer case out of the way to remove the transmission, you have to remove the shifter, disconnect the drive shafts from the differentials, and then pull the transfer case & driveshafts backwards as a complete assembly - slip and allow either driveshaft slip yoke to pull out of the case and you have an oily mess to clean up. Or, you could drain the transfer case, so that the drive shafts can be safely removed without making a mess, pull it back and suspend it - but at that point, why are you even leaving the transfer case in place, you might as well unplug the cables and take it down.
And please note - we have not yet touched on the subject of being able separate the transfer case from the transmission - according to the service manual, you can take the transfer case out and leave the transmission, so you do have the option of separating them or removing them as a unit - which ever is more convenient - if you have access to a transmission jack, it would probably be easier to take them down together.