@BigRedConsultingto answer your questions directly, the shift key works on other windows, but not on the edit window.

I've been using QuickBooks since Windows 3.1 and the edit window has always been resizable. It has to be resizable in order to be usable.  It was resizable last month.

It doesn't matter which item one edits - the window is always locked at a width that is wider than the QB window and multiple times the height of the physical screen.

Changing to a different company file has no effect.