Okay, this works for me:

version: 1
imports: []
schemas:
  - id: monolith
    title: monolith
    parent: root
    children:
      - id: tickets
        title: tickets
        namespace: true
        children:
          - pattern: '*'
            template: templates.ticket

I was able to create

monolith.tickets.foo.123

and it applied the template