I had a one-off requirement for a slide deck for something, and I really don't think in that form - so I ended up writing a detailed outline in markdown, using

I had a one-off requirement for a slide deck for something, and I really don't think in that form - so I ended up writing a detailed outline in markdown, using pandoc to turn that into pptx, and then checking that in libreoffice. Worked surprisingly well; I didn't have a style to conform to (so I don't know how well libreoffice handled those) but the defaults worked out.