Recording a window that's not full screen in OBS is challenging because if you use the Window Capture source type, it won't capture any of the menus or popup windows, it will literally only capture the one window you preselect.
In this video, I show you how to use a utility called sizer to accurately size and position a window, then how to use the Display Capture source to accurately crop to the window. Perfectly cropped windows that capture all menus and popup windows.