Thank you so much for looking into and considering if that's possible. Yes, I have felt that's the one and only thing that Things handles better - projects. But if the drag drop onto smart lists could happen, then GoodTask would be much better because it's so much ore powerful and flexible.
I use a GTD methodology where whenever there's two or more related tasks, then they become a project, particularly if they are sequential. So a simple project could be buying a new computer. The steps might include researching online, visiting the Apple Store, getting some recommendations, etc. A more complex project could be performing some work for a client. But even that could be broken down into smaller projects - bidding on the project, writing up an agreement, creating a prototype etc. In a GTD system, projects need to be small enough that projects can be finished in days or weeks, not months. So you end up with lots of them.