Provide output of 'sudo blkid'
Then tell us what partition is KaOS /boot partition and KaOS root partition (sda6?)
Also what is manjaro /boot/efi partition and windows EFI partition (sda1?).
I assume you want to use Manjaro grub to boot KaOS. Tell us if it is not so (more dificult to use KaOS systemd-boot to boot all other OS if their EFI partition is not the same partition as KaOS, but can be done).