How to add a new placeholder in the Email Template?

Is this possible to deactivate a particular workflow?

Due to some reason, fetching emails with php bin/console uvdesk:refresh-mailbox my_email works but it does not create tickets in the helpdesk

As I can check by default refresh mailbox is fetching the ticket for one day only. how to refresh it for a particular time frame?

Please suggest how we can permantly delete the tickets? or make deleted ticket restore.