Scrivener because... I don't know why really.
But I refuse to use microslop, and having to manually manage files gets annoying, so no onlyOffice, etc.
I can't use markdown for my current strory because I have tables with merged columns, which markdown cannot do (as far as I know), so no markdown based apps.
I can not use online services because I am a paranoid Linux user with a homeserver, so that's out too.
And now, all that is left is... scrivener, and a few scrivener alternatives (like novelwriter if I remember correctly) that I cannot migrate to because scrivener export functions suck
And I don't hate myself enough to use latex