How can I delete Candidate Dimension Source names?

We are looking to downsize our Candidate Source Names list. I have found a doc that outlines to go to Candidate Dimension Source Names> Highlight the source> click the 'X' to delete the source that is highlighted. However, when I click on the source name the 'X' does not appear, and I am unable to remove the items that we are looking to remove. I attempted to raise an SR and was sent here instead.