Well, a bit late now but you could have printed a slot for the panel to slide into. Alternatively you could use some white U channel to hold the window.
Its not too late :D. I can alway print/add to make something work. The window is really large so I can sacrifice some of that space if means getting a good door/mechanism on moving the window. I see what your saying on white u channel but would be a little hard to slide it out if I'm imagining the same setup as you with it.