Is there any difference between these two options to need both entries?
The "Customize this Parking position" will open the customization editor at the parking spot you are already parked in, and it's only available when you are parked.
The "Customize Airport Positions" is always available even if you are outside a parking spot, and doesn't open on a specific parking spot so, it might be more useful if, for example, you just landed and found a parking you wanted to use is labeled as "Too Small", so you can fix that before even getting there.
