No machine has a magical drain plug for the hydraulics as far as i'm aware. If you want to do an oil change, the way i do it is to run the machine at idle, attach a hose to the aux hydraulics and operate it till it starts to get noisy and jitter. Shut down, re-fill. That gets as much oil out as possible.
If you have a contaminated system, especially water, i'd drain it, give it say 5-10 litres of oil, drive it around, lifitng/tilting to get the fresh oil through the system, drain it again. Repeat till its clean, then top off the tank.
Others have said this way is a bad idea as it runs the pumps dry, but it never gets dry, there is always oil residue. If you keep running it while its drained yes, it will be damaged.