ansible_nested_dict_kindof_subelements.yml

- vars:
 ansible_added_line: "# Line added by ansible "
 nofile_limits:
   - user: root
     limits:
       - soft: 65001
       - hard: 70001
   - user: some_user
     limits:
      - soft: 65001
      - hard: 65001
      
- tasks:

 - name: remove old limits
  lineinfile:
     dest: /etc/security/limits.conf
     regexp: "^{{ item.0.user }}\\s+{{ item.1.keys()[0] }}\\s+nofile\\s+(?!{{ item.1[item.1.keys()[0]] }} {{ ansible_added_line}})"
     state: absent
  with_subelements:
     - "{{ nofile_limits }}"
     - limits

 - name: add limits
  lineinfile:
     dest: /etc/security/limits.conf
     state: present
     line: "{{ item.0.user }} {{ item.1.keys()[0] }} nofile {{ item.1[item.1.keys()[0]] }} {{ ansible_added_line}}"
  with_subelements:
     - "{{ nofile_limits }}"
     - limits