I would at least lay it down on floor so it's not a projectile when you slam on the brakes, or worse.
It looks like it's in a slide. You want to be careful about putting anything to long through the floor that might bind or rub when slide is going in or out. Maybe put a cleat and a hook to connect the table to the wall under the window.
Bill & Brigitte
06 Windsor PEQ, Cummins 400 ISL
2014 Honda CRV