You can put the BH on blocks so there's no pressure on any of the cylinders. If there's pressure on the cylinders the valve stack will probably leak a little and then it'll put pressure into the quick connects. But even without that if the ambient temp rises significantly between when you remove the BH and when you put it on, the hydraulic fluid's expansion will make it impossible to operate the quick connects. Plugging the BH side connects together when you remove the BH won't help that... in fact it'll be hard or impossible to disconnect them.
You can make a pressure release device with a tee that has quick connects on two ends and a valve on the other. Plug that in to the BH's quick connects when you remove it and use the valve to release the pressure before removing the tee device and plugging the BH in to the tractor.
They make connect under pressure quick connects but the ones I have take much more force to connect than regular QCs. Maybe if they were on a bulkhead they'd be useable but with my BH setup the QCs are on hoses and I just can't get them to connect.
