I was able to modify the menu by adding these lines to /boot/grub2/user.cfg, replacing the respective <MENU-UUID>
for each entry:
# Add Windows 11 Pro Menu Entry as First Menu Item
menuentry 'Windows 11 Pro' --class windows {
search --fs-uuid --no-floppy --set=root <MENU1-UUID>
chainloader (${root})/efi/Microsoft/Boot/bootmgfw.efi
}
# Add WinPE 11 Menu Entry as Second Menu Item
menuentry 'WinPE 11' --class windows {
search --fs-uuid --no-floppy --set=root <MENU2-UUID>
chainloader (${root})/efi/Microsoft/Boot/bootmgfw.efi
}
# Set Third Menu Item as Default
set default=2