FSNotes is modern text editor (like nvALT) on steroids.
FSNotes respect open formats: plain/text, markdown, rtf, and stores data in file system. You can view, edit, copy data in favourite external editor and see live result in FSNotes.
Markdown eidtor highlight code blocks on 170 languages, inline images available too.
Swift 4, open source.
the only fast and simple note app I know of, that has code highlighting and a very nice markdown supportVadim has used this product for one day.
Fast, open-source, supports RTF, multiple note source directories, super-responsive developer; syncs with iOS version.Cons:
This is a power-user's note app, built for speed, speed, speed.Marmaladesoul has used this product for one month.