Hi,
I installed Clear Linux to my fourth hard drive. The EFI boot partition was created correctly, but I was not able to boot, because there were still old bootloaders on this hd (grub and windows). I finally was able to remove them (I googled the correct way for my old bootloaders) and now I am able to use my uefi bios boot menu to select the windows boot manager on my first hd or the linux boot manager on my fourth hd like I intended to do.