Can I ask why you need to depressurise the system? Is there a specific job you are doing?
You will need to raise car to highest setting, remove LDS tank cap, support the car safely on axle stands at the jacking points (don’t use the subframe).
Then you can lower the suspension to the lowest setting, lower driver window and ensure bonnet is raised.
Close all doors and leave the car for 5 minutes without opening doors or pressing switches to allow car ECUs to memorise settings and go to sleep mode.
Then disconnect battery negative and ensure it cannot reconnect accidentally.
Then you can depressurise the axle(s) you need to work on depending on what you want to do. Discard any LDS fluid that may come out and don’t reuse,
When finished you will need to tighten bleed valves, top up the LDS reservoir to between the min and max marks as shown on the outer tanks markings:
The system may well need to be primed by applying some pressure into the reservoir. Again ensure all doors are shut and reconnect the battery. The pump may try to engage.
Leave the car for a few minutes to allow the BSI and ECUs to wake up and initialise without opening any doors.
After a few minutes you can start the car and put the suspension back to normal first of all. It may take some time to raise the car. If it does, you won’t have to apply pressure. Then you can raise it right up to max and allow the car to stabilise at the highest setting.
Remove your axle stands and proceed to bleeding the circuit.
From highest position, lower car to lowest position. With engine still running, SLOWLY turn from lock to lock 10 times and do not hold the steering on the full lock either way, return steering to ahead position
After this, top up LDS to between min and max levels if necessary and watch for any bubbling. If there is bubbling, allow the bubbles to disappear the repeat the raising, lowering of suspension one more time and do the lock to lock another 5 times slowly. Repeat checks for bubbles and repeat until there are none.