Custom Properties Question

I’m using “custom properties” to control the different meshes that make up all of the movable widgets on a car. Door open/close, window up/down, door locks, wipers, lights, brights, etc. Its a longer list than you would think. (FYI I want to keep the car as different meshes).

The problem is that I can’t see all of the “custom properties” controls at once. They only display when each separate mesh is selected. I want to be able to adjust them all together from one panel. Any addons or nodes out there to help with this? (Hoping not to use a mesh based picker).