Is There a Way to Customize Theme Viewers?

There's not a ton of different fans you can use, not a lot of themes to choose from. They don't have any context manues in the cue. There is a short cuts action to get articles into matter, but there's nothing to get things out of it. It'd be nice if you could export, for instance, a an articles high lights as a mark down file and imported to other textae that you want whether it's like a wrider or bearer or whatever it happens to be.