Today I wanted to install some packages using Yast, clicked “Software”, and, after system scanned installed packages, I got list of some kernel packages that are installed but retracted. What to do with them? They are: “kernel-default - The Standard Kernel”, “kernel-default-extra - The Standard Kernel - Unsupported kernel modules” Aand “kernel-default-optional - The Standard Kernel - Optional kernel modules”.
It is up to you. This kernel was removed because it caused issues for some users (hardware dependent). You are either using this kernel and do not have any problems or you are not using this kernel anyway. In both cases there is no pressing need to do anything.
I tried to remove the retracted packages from a system where id not not use it (I reverted to an older kernel because this system was hit by the problems mentioned), but run into problems. I think it is better to wait for the next kernel update (it is already there), and then until it is removed from your system by the normal procedure (that only keeps a limited number of kernels).