[SpiralOcean]

You can nest projects. Although I don't think OmniFocus calls them nested projects. They call them action groupings.

The dragged projects you describe, are actions until they have children actions. Then they turn into action groupings (nested projects).

I use nested projects frequently. When I get to an action that I can't move foreword on because it needs other actions done to complete it, I create child actions, a nested project.

Working in OmniFocus becomes a way of thinking, brainstorming and learning.