Been watching this thread for a 'storable' creeper seat like the OP asked but I'm not sure one exists. There is the 'Z' creeper that lays flat and folds into a seat but the only one of those I've had didn't last a year before it was falling apart everywhere and would not recommend.
FWIW my neighbor uses one of these, that the first time I saw it I thought it looked like some ridiculous frankenstein thing he'd patched together but was impressed on how he's able to quickly go from sitting on it to standing on it to switch between working in a wheelwell and then up under the hood and back while his truck is up on stands. Then I saw it one day at one of the big box stores (Home depot?) one day and realized it wasn't just some DIY hack of his. It's a Pro-LifT C-2800. Just mentioning it as it's been on my list of wants for a while now and could possible envision it as a space saver if you also have a want/need for a short stool in the garage or whatnot.
