Try changing your desktop resolution or adjust the scaling of the windows in Windows OS to reset the application's display mode. I've tested the demo version of the application and it works normally. If you can back up the menu that you've created and then reinstall the software, but make sure the main installation folder is deleted from Program Files. Reinstall the product and import your menu, then the bottom frame will be accessible again.
You can obtain the demo from the download page at Software Informer, but this means you already have the registration number to activate the program in case it will be displayed as demo: http://ultramenu.software.informer.com/download/