Simple example for composing complex vars by generating YAML using an inline template

gistfile1.txt

---
- hosts: localhost
  gather_facts: no
  tasks:
    - name: do some stuff
      vars:
        temp_var: |
          {% for i in range(1, 5) %}
          - {{ i }}
          {% endfor %}
      debug:
        msg: '{{ temp_var | from_yaml }}'

This playbook dynamically creates a list in YAML using jinja templating, and then uses | from_yaml to convert that YAML to native types. You could alternatively have the content of the temp_var variable in a separate .j2 file and then use

{{ lookup('template', 'path/to/template.j2') | from_yaml }}