There is a part that Lippert offers that allows you to control each slide individually, sorta. It basically allows you to turn off pressure to each hydraulic ram. There are a couple of problems that I see with it.
1. you would have to run new hydraulic hoses from this device to each hydraulic ram on the slides.
2. this would mount close to your hydraulic pump so to likely in a basement type area. And since this is just an on\off button you would have to open whatever slide you want, run down and change the valves for each slide after that. That would be a pain.
Edit: here is a link to what I was talking about