Q: What should I do if my paper is with the journal for 13 months and the editor is unresponsive?

Thirteen months is a long time, and your paper hasn't made any progress with the journal. Therefore, I think it would be best to withdraw your paper without wasting any more time. Please send a withdrawal letter to the journal mentioning your manuscript ID and submission date and request a confirmation of withdrawal from the journal editor. Do not submit elsewhere before you receive this confirmation, else it will be considered a duplicate submission. 

In case the editor does not respond to your withdrawal email or does not send a confirmation, you should send 2-3 reminders. If there is still no response, you will have to write to the journal saying that you will consider the withdrawal process complete if there is no reply within a specific time (set a deadline of around a week).

If you still don't receive a confirmation, send a final email stating that since all your efforts at contacting the journal have failed, you are considering your manuscript "unsubmitted" from this journal. You can then submit your manuscript to another journal. 

Related reading:

• Should I withdraw my paper if the status is showing "Editor invited" for several months?
• What to do if the journal is not responding to my withdrawal email for a submitted paper?
• How to write a withdrawal letter to the journal