Using the option "Subscriptions > (mysite) > Websites and domains > FTP Access" I can add up to 2 additional FTP accounts (in addition to the first one) which I can use to point to other folders in the same space, so those users don't have access to the whole subdomain, just an specific folder. That's a total of 3 FTP accounts.
But how can I add more than 3 FTP accounts? After adding the third one, the button to add another FTP account disappears and there is only the Remove button to remove an account. If I remove one account of the three, the "Add" button comes back.
So there is a limit of 3 FTP accounts in my Plesk. How can I change this limit? (I do have root access to the server if necessary).