Yeah, when the Project panel or Bin panel is arranged to be wide rather than tall, it does leave a lot of unused space.
We can show or hide the Preview Area (Project/Bin tab pop-up menu > Preview Area), but are you thinking that it would be helpful to maximize or minimize the vertical height (in the same way we can maximize and minimize Video Tracks and Audio Tracks in the Timeline) when the Preview Area is showing?
I've always thought that the Preview Area should be in the Info Panel, but I get that it is meant to provide similarity to the Poster Preview found at the top of the Project panel in Adobe After Effects.