Doing too many things at once
I love the whole fountain/markdown idea and this program initially showed great promise (despite the many bugs along the way). It began as a file converter and it does an okay job of that.
The promise was that you could edit a screenplay.fountain file in your favorite text editor, then open that file in Highland and view your screenplay as a pdf. This works, until you go back to your text editor, write a few more pages, and then attempt to view them in Highland. No dice. The changes you make in your text editor will not appear in Highland unless you exit Highland and reload the file. This is cumbersome to say the least.
This would not be a problem if you could run Highland from the command line, because then you could simply run a script calling Highland from within your text editor, and the new pdf would pop up in whatever pdf viewer you are using, but until then no joy working in your favorite text editor and using Highland.
Instead the developers clearly now envision people working in the Highland toy text editor (whose most advanced features are bi-color syntax highlighting and find and replace) and viewing their changes in the Highland viewer. If thats what you want, the program does it.
BartlebyScrivener about
Highland