How can I send a link to ONE user in a list to activate their subscription?
For example, if I add a user to a list on the backend and set the status to "waiting confirmation",
You can do this using Mass action. There is an action "Resend confirmation email", which can be used for this purpose
Under the "Actions Target" tab, you can use "AcyMailing field" action where you can match "email" with the specific user