I have a node type "Project", and users can add multiple tasks for this Project node. e.g. There is a Project named "Building website", it contains two tasks "Design" and "Code", and every Task has another two fields: time and budget.
The Field Group module can solve part of the problem, it can mix multiple fields into one field. But this mixed field amount can only be 1. That means I can only add one Task field in a Project, however I need add unlimited Task field to Project. Do you know any modules can do this job?