Wordperfect 5.1 with reveal codes open in a split screen. I used it to begin with for when I'd done something and couldn't figure out what I'd done, or where the bold mark was. But I ended up pretty much keeping it open for mark up, not that I knew what that was then.

I guess what I miss is the two open at once, you can preview in the wiki stuff, but not see what the marking is doing while you edit.

And that's WP for DOS, not windows, in the ideal world.