[ludwigschubert]

Are you thinking of Bike?

https://www.hogbaysoftware.com/bike/

(Maybe not — this isn’t markdown first; but it is a very macOS-y, keyboard driven, hierarchical outliner that I enjoy.)

[Ringz]

Bike looks very nice and it’s built on open file formats. I will try it out. Look at my edit above: it might be an old version of ginkgo. But I’m on my phone right now and can’t figure it out…