Possible to force all windows to open on primary display (Ubuntu 18.04)?

Ubuntu 18.04: Recently, “new window” selected files and folders intermittently open full-screen on my secondary display. Even when I right click on a folder and select “open in new window” it may or may not open on the secondary display, which is a bit smaller so the top of the window is off the screen. Is there a way to force all windows to open on the primary display? I have no problem dragging them to the secondary if that’s where I need them.