I installed Centos 8 on my Dell r440 the other day and enabled cockpit. I noticed right a way that Storage was not an option on the left pane. It turns put this is a separate package that needs installed. An easy fix and surprised it wasn’t part of the default install but if you run into it just enter the following:
# sudo yum install cockpit-storaged -y Thats it, easy peasey!
Now I have what I was looking for.