If you want to create a new Ticket from a message in an ongoing Ticket, you can easily do this with the feature New ticket from message. Click the three dots in the upper right corner in the specific message and then New ticket from message.

When you click New ticket from message, the warning text below pops up:

So, when you hit Save, the message will be deleted from the ongoing Ticket and moved to a new Ticket, with a unique Ticket ID. You will find the new Ticket in the Tickets overview and it will automatically get the status new.