pxe boot pass variable to submenu

I'm using RHEL 8 and I currently have the ability to install a single image the LAN. I'm trying to expand our options such that we can select from several images. I'd like to have a top level menu where I can select image A,B,C. Then it would call a submenu and pass in the selected imaged. The menus and submenus work but I cannot figure out how to pass a variable from the top level menu to the lower menu. For example if I want to pass image A into the submenu this is what I've tried.. BUILD="A" append pxelinux.cfg/Config BUILD="$BUILD" Then in the submenu menu being menu title BUILD="$BUILD" When I boot the system it does not show the variable it just prints BUILD="$BUILD" So my question is am I passing in the variable correctly? How do I display the variable in the menu?