Within Teamwork Desk, you can create a new ticket from a particular thread in an existing ticket.
While viewing a ticket, navigate to the reply you want to split into a new ticket. Click the three dots in the upper right of the reply and select Create New Ticket from the dropdown menu.
A modal will open allowing you to update the subject line for the new ticket.
If the original ticket reply has existing CC addresses included, these will be listed in the Create Ticket modal. The addresses will be excluded by default. You can use the toggles to the right of each address to include them in the newly created ticket.
Once you click Create, the new ticket will be added as an active ticket in the inbox where the original ticket was located.
For more information, see: Merging Tickets