In Halo you can use the parent-child relationship on tickets to maintain their status as related tasks or subtasks for an incident, project, request or otherwise.
Linking to a Parent Ticket
In any ticket hover over the 3 dots in the upper right of the inner window.
Click "Link to another Ticket":
This brings up the ticket search window.
Search for the ticket you're looking to link this one to.
See the guide on Halo Search Tools for advice on using this.
Select the ticket you wish to link the ticket to.
Click "Confirm Selection" to finish.
The ticket you have just selected is now the parent ticket of the one you browsed from. It will be listed under the child tickets tab in the ticket itself and the link will be shown in the child ticket.