This is exactly what I wanted

I love the simplicty and power of the Fountain syntax but I still want to feel like I’m working on a screenplay while I’m writing. Slugline is the best of both worlds, with nimble formatting conventions built into a beautifully simple canvas — you really can just write and Slugline takes care of the rest.

And the outlining features are incredibly useful. I can outline in the same document that I’m writing my screenplay in, simply and seamlessly. It’s amazing to watch your outline just become your screenplay over time. And you can easily choose to show or hide the outline material when you’re previewing/sharing your work, which is great for when a colleague giving feedback wants to see the scaffolding. I love it.

Lastly I just want to say that support for Slugline is phenomenal. The few times I’ve had to reach out via email for a question, I received a prompt, enthusiastic and helpful reply. Very impressed.

I went back and forth over the options that are out there for a while before deciding on Slugline, and I’m so glad I did. This really is exactly what I was looking for.

Darcy Fitzpatrick about Slugline, v1.1.1