I installed manjaro in uefi mood with windows 10. when i installed manaro i could detecte just the HDD so windows still on ssd. the problem when i boot the default alway windows and there is no menu to choose i have always to press F12 to access the booting manger.
I even notice that the booting of manjaro is quite slow than normal.
i used this ways but nothing worked:
1- edit the grub in /etc/default/grub with default=0 and comment out the GRUB_SAVEDEFAULT=true
2- i used $efibootmgr and i set manjaro first but after i reboot windows is set again the first like i changed nothing
3- i used this command:
$ sudo grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=manjaro --debug --recheck
all these and nothing worked, any help to solve this, especially that the system is slower then it should be
note my lapyop is acer NITRO 5 so i think it should be a bit faster

install perhaps "refind" https://www.rodsbooks.com/refind/ on the SSD ? If I remember, an EFI could not find correctly my HDD on a notebook few years ago (bad programming of it in the notebook? dont know). Then installed "refind" on the drive which boots (there is a way to do it under linux when you are booted in manjaro): it boot now in refind, show the HDD, choosing the HDD then return ,then it boots the HDD (with grub on it). I know.. 2 boot manager after each: not sooo funny.. but I dont boot the notebook often (3 times per week?). Then when you are in your grub.. you will probably can still go back in the windows. So, these are my thoughts for now.

You may have to go into your bios/firmware settings to change the boot order.