Hello @allison88 ,
Thank you for reaching out to the Instructure Community regarding your question concerning enabling Collaborations when the Canvas for Elementary theme is applied. Collaborations would not be visible to students in the Course navigation menu when the Canvas for Elementary theme is applied to a course. You cannot enable it under Course navigation in the Course settings, as you normally can, with a non-Canvas for Elementary themed course. We have a feature comparison document regarding Canvas for Elementary here as well, Canvas for Elementary Feature Comparison - Instructure Community . So, any materials students would access would be in the Modules, Schedule, or the Resources (external/LTI tools) tabs. Further, I might suggest, as a workaround, when adding a student to a Collaboration, they may still be able to access them via Groups, under their Global Navigation menu.
I hope this helps ! Again, thank you for reaching out to the Instructure Community.