Example2: a person is not linked to an organization yet and has only basic licenses or is just an account in data base cannot be added with error message 'this email address already belongs to another contact'.
The current workaround that we can provide is to:
1.Search for the person with his full email address
2.Click on Chat (if possible)
3.Click on profile
4.Click on Add Contact
5.Go to Contacts
6.Right click and Edit the email/phone number/etc.
Perhaps the error message might provide more information - 'account is pending activation' or 'you cannot edit the email of the person'.
Merging all add a contact option in the 'add a new contact' sub-menu would also be more intuitive
Edit: the exact setup where the workaround was used included restricted search options for the organization - contacts from different organizations were imported without other than the error message restrictions for editing.