There's a free storyboard program called "storyboarder" (duh). I used it a little (not for VNs) and I think it's quite versatile, even if it works better if you're an artist at heart.
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In addition to Grammarly, I use Hemingway Editor, which fits well the kind of writing style I want to keep.
Unfortunately, both Grammarly and HE destroy indentation, so I can't feed them code and get code in return.
I too am satisfied with Free Grammarly. The paid options do not attract me much (just sometimes a mild curiosity about some of its "advanced" suggestions), if I'll ever buy it, it'll be out of sheer gratitude for a tool that I simply can't do without.
To answer the OP, I write pseudo-code (it looks more or less like Nicke's one) in Google Docs (this is because I need to access it from different places and share it with other team-members), then fix it in Editra. Yeah, Atom is much better, but I'm too used to Editra.