Hey @Dario11 , my honest response would be “this is not MS Project - sub-subsubtasks is not a good idea”. I understand they may not like that response but trust me, it will not work. You can find other ways of categorizing a project by using Sections and optionally, Subsections using the Group button.
There is also this suggestion from @lpb.
However, I think there might be plans for Asana to add expansion for a further level of subtasks to be viewed in the Gantt view or List view - can’t be certain though as they do not make their roadmap entirely public, unless you join the Ambassador program where you will get early previews of upcoming features and live webinars and events.
Btw, I have moved our discussion into this existing thread where you and others can vote on (scroll to the top, click on the Vote button, top left), since it was not quite related to the previous thread you initially posted on.