Vertical slides with level 2: how to keep showing level 1 heading? (reveal.js via pandoc)

[ppenguin]

I couldn't find out how to get vertical slides (for level 2 headings) while keeping the level 1 heading statically shown, even though IMO it should be the default (or at least easy to achieve).

I'm using pandoc with my slides as Markdown, with a slightly customised pandoc template, and a much more customised css to get rid of a lot of the default centering stuff.

Also I'd need a way to not show an empty slide with every new level 1 heading, i.e. I want to immediately show a level2 slide (as the first vertical slide of a vertical stack) for every new stack.