Link a skill to the job, degree or certification where you used or earned it. A link never goes away on its own, and you cannot delete one: instead, untick "Shown" to keep the skill off resumes for that one entry while the link stays visible here. Resumes and cover letters only list skills that have at least one visible link, so a skill with no visible link shows a "Not linked" badge and stays off them until you link it or show one of its links.
Related
Still stuck? Report a bug or request a feature.