I’m trying to get a couple of tubes in the transmission as a temporary measure. I read somewhere that the car has to be running and jacked up one side so the transmission oil doesn’t drip out when the bung is removed?
Does this sound right before I attempt it? 2010 MY Vogue SE TDV8 3.6 Stornoway Grey- fully loaded

I would say it definitely has to be running as that's when the level is correct. If it's not running, oil will come out.
I put a couple of tubes in my old Jag last year but did it when adding new oil as part of an oil change.
Hope it has the desired result for you.

If you have a couple of ramps place them drivers side front and back and drive up them a little bit if not then use a kerb. Yes the engine must be running when you remove the filler plug it only takes 5 mins