In the new UI, the theme can be changed in the theme editor under the Admin panel. When changing the theme, it appears that it's only possible to edit the two currently available themes -- Canvas Default and K12 Theme. It would be nice to be able to add new templates so that we are not modifying the Canvas Default theme. It would keep our institution template separate from the Canvas Default template. It would allow us to switch between templates that have already been set up in advance if we want (say for a school spirit month, or a holiday).
Also, it would be nice to be able to copy the attributes from one theme to another. For example, the "Add a New Theme Template" is added to Canvas, it would be nice to copy the currently modified template (e.g. colors, logo, favicon) to a newly created template, so that we don't have to perform additional work on the new template.