Cannot Disable User

I got a warning that I am maxed on on users, but I have a couple inactive users that I would like to convert to new active ones. I tried Removing the inactive users, but get a message that they have authored content, and so cannot be deleted but can be disabled. I cannot find the disable button / checkbox.

Please advise what I can do to "free up" these licenses. The accounts in question are in no groups, but this does not cause Confluence to see them as inactive and allow me to use their license.

Please advise.

Kind regards,
Rick Cogley