@george1421 Sorry for the late reply. The menu entry does work now. We have sda and sdb drives in our computers and wish to specify the sda drive for all the imaging with a parameter. The images are captured in single disk.
Edit: just to specify the idea behind the 2 drives. We have computers that students are using where sdb is always a Windows 10 image but the sda serves as “playground hard drive” where students can install anything they want. We intend to create premade ipxe entries for the deployment of different operating systems and can now do it thanks to your help. This sda/sdb targeting is the only thing we were left wondering about.