Another topic is already opened, see:
https://forum.asana.com/t/project-folders/
As subtasks are not easy to use I would also appreciate to group some projects. For project with several members involved (research, marketing, finance,…), having only one project with sections leads to a very long list of tasks, even too long… For this reason we have already doubled some projects but not ideal because the project’s list becomes long. Thus for very big project we have decided to convert the project into a team.