In the notification method panel there is an option to have supplementary email address and there is a hint about using a TAG:
I tried to use this <OTRS_TICKET_DynamicField_agentEmails>You can use OTRS-tags like <OTRS_TICKET_DynamicField_...> to insert values from the current ticket.
agentEmails is a dynamic field of type ticket - multiselect, as I would like to select agents to have their email added. The field is set in a process ticket.
This would allow to keep theses agents informed about the ticket process even if they don't have a full access to the queue. But right now, I don't see the notification going out. (By checking the ticket history)