[Feature request] create posibility of adding child-list to existing list

[dawciobiel]

Is your feature request related to a problem? Please describe.
When creating a list consisting of TODO elements - everything works fine.
However, I would like to create sub-lists. That is a child-list to existing lists.
E.g:

• Create a great application
  • create application GUI
  • create a back-end application
  • create ...
• Go for shopping
  • buy a bread
  • buy a dog
  • create a hot-dog