Pulling the file "ApplicationTemplate.touchgfx.part into the editor and manually tweaking the screen width value after doing generate code inside CubeMX enabled editing without having to put up with that 32 pixel dead-zone in the editor.

That image looks like what I got when I attached a bigger display (and the screen pixel width and height changed), so check the width/height pixel counts. It also doesn't hurt to do a review on the front & back porch values etc....and make sure yo...