Assuming “Drive 1” and “Drive 2” are actual disks and not partitions:
1. Physically disconnect the Manjaro Drive 1 disk.
2. Install Windows 11 however you wish on the Drive 2 disk.
3. When finished, reconnect the Manjaro Drive 1 disk.
4. Boot immediately to BIOS and make sure Manjaro Disk 1 is first in boot order.
5. Reboot – os-prober should automatically detect the new Microsoft EFI boot files on Disk 2 – which means that Windows will then show in the Grub2 menu.
By disconnecting the other drive before installing another OS such as Windows, the Manjaro disk is obviously isolated from the Windows Setup process (Safe).
I hope this helps. Cheers.
A tutorial I previously wrote extends on this greatly. Several important caveats are mentioned that should also be addressed when multibooting Manjaro and Windows.