A week or two ago I spent about 10 minutes experimenting with OO styles. It's worth learning how they work.

Styles seemed buggy at first, but that was due to assumptions I made that were wrong.

Simon wrote:

OmniOutliner is very good. If you're also looking to go mobile it is the
most powerful outliner you can get. Yes it has some quirks; styling; but
once you learn how it works it's superb. One of my most used apps.