I have ran the same problem and couldn’t solve it. I wish OF had fully functional nested projects so we could maintain the structure and show only the next action in a sequential subproject.
To circumvent this lack of functionality, I just put a daily task which says ‘brain dump’ and then I have a separate ‘brain dump’ project (checklist or template) in a ‘waiting’ status (so that it doesn’t show on the forecast list or other perspectives) with the full brain dump routine and structure . So when and I am ready to do the ‘brain dump’ I manually go to the template and create a new instance (duplicate) and start checking it off. Just the same as a packing list for travel or other routines.
I suppose you can link the brain dump task to the brain dump project with a link, to save a couple of clicks.
I also use some workarounds (in my case: each day in the morning I duplicate “BrainDump - template” project), but IMHO it would be more universal to find some technical solution for filtering out subtasks from the view. In custom perspective we can set:
Group and Sort: Entire Projects
what works quite well, but it’s not available in the Forecast perspective…