For example, I have a ‘Writing’ list that I would typically have divided into several sections such as ‘Admin’, ‘Articles’, ‘Novels’, ‘Short Stories’, etc, with my action items listed beneath each heading. I’d prefer they weren’t in separate lists because the items are all related and I might need to refer to them within the same list. This would be purely for organisational purposes.

For inspiration, see how the Things app or even Reminders handles this feature.