Sterling Plastics (and I guess Tupperware) make totes with wheels that are designed to roll under beds to provide storage for that space. If you have cabinet doors, you can purchase "wheeled totes" that roll through the cabinet door and into the space under the dinette seats. All you need to so is to lift the end of the tote to clear the cabinet door lip, then just roll it out.
What we found when we had a dinette, was even with a sliding tray, what you can put on the tray is limited by the height of the cabinet door opening. So, when packing for a trip, we'd be forced to store some lightweight things (paper towels, toilet paper, paper cups, etc) on top of the totes.
So, in reality, we would, far too often, wind up having to "unload the top of the sliding tray so we could pull it out. So, essentially, what we wound up doing, was having to open the bench top so we could move stuff so we could slide the tray through the door. We found, that what really happened, is we lost the space below the sliding tray and we were still opening the seat from the top to make room to use it, so we just got what we wanted off the sliding tray while the bench top was open....
Sort of a "catch 22" situation, having to remove the bench cushion and plywood to move things so you could open the cabinet door in the end of the bench so you could slide the tray through the opening without knocking stuff off the tray which would force you to remove the bench top to pick that stuff up so you could push the sliding tray back into the cabinet.....