how to clear boot section lines

How can I clean up old boot section line within grub2 (Yast)
I see now multiple boot section lines in the menu when I startup opensuse Leap 15.2

You can try running

grub2-mkconfig -o /boot/grub2/grub.cfg

to generate a new menu. But I don’t know enough about what you are trying to do, so I’m not sure if that will solve your problem.

You could turn off the probing for other operating systems with Yast bootloader. But again, I can’t tell whether that is your problem.

Maybe you could provide some more detail on what you are wanting to do.