Hello! Currently it is not possible to create sub-groups or sub-request types in Jira Service Desk. One way to implement something like this would be to use a field to indicate the sub-group that the issue belongs to. Please check this other similar question:
I hope this helps.
Hello Atlassian Community! We’re thrilled to announce some exciting changes to incident management in Jira Service Management Cloud, in order to give your teams extra muscle during incidents, and ...
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events