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 Child Tickets
In any ticket hover over the 3 dots in the upper-right of the inner ticket window.
Click "Link Tickets to this Ticket":
This brings up the ticket search window.
Search for the ticket(s) you're looking to link to this one
See the guide on Search Tools in Halo for further detail on using this screen.
Select the ticket(s) you wish to link.
Click "Confirm Selection" to finish.
The ticket you have just selected is now the parent ticket of the one you browsed from. The ticket you originally worked from will be listed under the child tickets tab in the parent ticket. There will also be a clickable link to the parent ticket in the child ticket.