store aircraft/car in svw
1: Call out any aircraft/car
2: go on foot in your facility
3: drive your bmx behind the keypad (press A and Y for driving/stop only, don't use rt or you will spawn outside with your bmx)
4: make sure you will spawn on your bmx when you press Y or triangle
5: press Y and A at the same time
6: drive the bmx to a full garage and replace it with a bmx. Make sure the bike rack is full with bmx's
7: your aircraft/car is on a bike rack in your garage now. Do the same steps with a sv now and overwrite it with your aircraft.
8: your aircraft is now in your svw
If you want to keep your sv you have to do it a third time, call out an rh8 from any garage and overwrite it with your sv on the bike rack. Your sv are invisible and not callable in all garages but not in your facility.
If you don't need your sv anymore just get a street bmx and drive it to the garage and replace it over your sv.
If you want to be sure that you won't lose your aircraft make your Hangar full with buzzards from the CEO interaction menu then call out your aircraft from svw and fly it to your hangar. Except the full alert and replace it over a buzzard. You will have a dupe of your aircraft now. One in your hangar one in your svw. you can also use this method to make some cash. You can keep the duped aircraft and sell the original.
If you store any car in your svw you can easily swap them with any car in your garage. Just drive with the car from the svw to a full garage and choose the car you want to swap.