Can you create Sub-Lists or Group Lists under a heading?

[LNHelps]

I'm looking to create a board that has 5 themes and 3 lists under each of these themes.

I have currently just created 15 separate lists but would like a way to simplify the view. Is there a way to do this?

[Hannah Humbert - Simpla Workflows]

How about something like this with card covers?

[Iain Dooley]

@LNHelps one option is to use labels for your "sub-lists", then you can hit the "f" key to quickly show only those cards.

The only other thing I can think of would be putting your sub-lists as cards and then using checklists on those cards for each of your actual items.

Beyond that there are no "nested list" structures in Trello.