The short answer is that it depends on what you want to output. Atom has no standard framework for handling views, so anything can be used that suits your needs. If you just want to output a table of data, you might be able to get by with straightforward DOM manipulation. I’m not an expert on view frameworks, but for a newbie, Etch is probably the best place to start, as something with a low learning curve that mostly seeks to minimize the amount of messing with the DOM you have to do.
Now, for the second part of the question, we can look at
markdown-plus to observe how it creates its pane. It starts with @toggle.