My system has the following drives: a 500GB SSD, a 2TB HDD, and a 32GB Optane card. I'm running Debian 10 from a partition on the SSD (sda), and Windows 10 from the HDD+Optane Intel RST RAID drive (sdb).
Currently I switch between Debian and Win10 by pressing F8 on startup or changing the BIOS setup. I know that grub should be able to show me all the bootup options though. I have looked into grub-customizer but couldn't figure it out. How can I add the Win10 boot option from the different drive into the grub options?