Some of us have multiple instances of Manjaro, say Manjaro KDE, Manjaro LXQT, and so on. In UEFI, there is only one 'manjaro' bootorder and that would be latest that is installed or have its grub most recently updated. Some of us would like to have all the various bootorder listed so we can boot into the respective Manjaro editions through boot set up. Most, almost all, have 1 $esp and that is quite right too.
To circumvent this issue, some of us use custom (usually custom_40 - but I'd recommend custom.cfg, as in custom_41) and add entries that uses configfile or multiboot. I personally don't do this, I even disable os-prober, because I have my own grub and all my entries are there without being affected by anything outside it. And this is not what I'm addressing in this topic. Just the point that there is only one 'manjaro' bootorder regardless of the number of Manjaro OS's we have.
To have multiple bootorders, at each Manjaro OS, create an additional directory within the $esp, so say at Manjaro KDE,
sudo cp /boot/grub/x86_64-efi/core.efi /boot/efi/EFI/manjaro-kde/grubx64.efi
Do that at all other Manjaro's and we'll have /boot/efi/EFI/manjaro-lxqt/grubx64.efi and so on.
Note that /boot/efi/EFI/manjaro/grubx64.efi will remain and that will continue to be latest manjaro that is updated/installed. And do not change the naming of grubx64.efi because that is what EFISTUB will pick up (and also used by systemd-boot and rEFInd - ).
One additional advantage of doing this is that we can set our preferred manjaro bootorder as the default bootorder (efibootmgr -o xxxx,yyyyy...) without hassles.
Hope this is useful to some of us (most do not need this, with one Manjaro - and not useful to me ). Also it is applicable to other likewise distro's like Ubuntu and Linux Mint (which uses (ubuntu/grubx64.efi) and so on.
 - It is not advisable to use systemd-boot and rEFInd if we want multiple 'same' distros - Arch and Antergos for example - irrespective of this bootorder issue.