Hi @Katrina-Hess, we use primarily the theming option to upload a CSS stylesheet and JS file for 90% of our customization. There is sometimes some additional external CSS or JS brought into the page as well, but that all occurs via the scripts in the theme custom JS upload.
Just to expand a bit on what the need is: we do a lot of custom layout styling and widget creation, and we try to keep it so that the instructor has to use as little HTML as possible. So while a lot of our custom code can be scoped directly by class or ID to the widget or layout being implemented, we also have "global" styles to set things like line-height or box-sizing in the content the instructor puts in. Through trial and error, we have found that the user_content class wrapper in Canvas pages is the most reliable way to significantly reduce, if not eliminate, the risk of our CSS/JS conflicting undesirably with native Canvas UI elements.
The user_content wrapper appears to be included on pages, assignments, and, until the redesign, discussions (which are our primary content type concerns) as a default wrapper for content introduced by the editor. I believe on discussions it also is introduced on all replies, but our real need is centered on the initial discussion post, where our instructors are accustomed to including our custom layouts and widgets (for example, a custom "case study" layout widget to display content the instructor wants students to consider and formulate responses about in the discussion replies). We are not concerned about those custom widgets and styling being available in replies, since we do not make the code available to students and instructors do not generally craft complex HTML for discussion replies after the initial post.
That's overall our use case for the user_content class on discussion posts. We would also be happy to modify our custom code elements to use a new class or ID that wraps the same type of content, but currently there does not appear to be a wrapper that 1) that wraps only the editor content and not surrounding UI elements, 2) has a consistent, human-readable class or ID name rather than a React class identifier.
I'm happy to clarify further if needed. I realize our implementation is a bit unusual and the level of customization we do is definitely an edge case for Canvas, but this would be a huge help to us if it is a possibility on the development end.
