[FEATURE]: Edit entire yaml file, and select from sections

[JamesPHoughton]

User Story

As an experiment designer, i want to be able to load the entire yaml file in the editor window, and select which section to edit/work on in the timeline/preview window, so that I can easily see how all of the components relate to one another, and be able to edit everything about the experiment

Feature description

I'd like the yaml editor to load up an entire treatment file, including intro sequences, multiple treatments, and (eventually) templates (which are not yet implemented).

Features

• a way to switch between major sections that can be rendered, ie, an intro step, or a specific treatment
• possibly a way to "collapse" chunks of the yaml in the editor window in an obvious way, and "uncollapse" them when I want to. [FEATURE]: Create collapsable/uncollapsable chunks of YAML #82
• if I switch between treatments that have the same stage names, and I'm currently viewing one of the named stages in the preview window, I should be able to see the differences between stages

What would this feature enable?

Eventually will allow us to handle multiple treatments in a single file in a graceful way.

Priority

Convenience for researchers