There are only a couple and taking of wheelchairs is not a big concern. I would not leave anything of value in it and do be aware that CMs move strollers and wheelchairs to keep the parking areas tidy.
Tomorrowland Trandit Authority - station is on the second floor, up a steep moving walkway that is not wheelchair accessible. Wheelchairs are left at the stroller parking just below.
Pirates of the Caribbean - it is preferred that guests park their wheelchair with the strollers and use an attraction wheelchair if they can't walk in line. This is because it is difficult to get personal wheelchairs from the boarding area to the unload area in time. Guests who can't use an attraction wheelchair may be able to bring their own to the boarding area - this depends on staffing at the time.
Swiss Family Robinson Treehouse - most guests using wheelchairs choose not to do this attraction because it involves many flights of stairs. If you do it, the wheelchair will be parked with the strollers.
Spaceship Earth - wheelchairs are left in the waiting area for guests with specisl needs, which is always with a CM around. Guests who can't walk can bring their wheelchair to the boarding area, but in general they are parked at the waiting area.