I am working on class project to build integrated messenger into Canvas including scheduler in it.
I don't know if one exists. Someone will have to build it, and I highly doubt Instructure will as they don't use XD for their internal mockup of the Canvas apps. If I find one, I'll post back, but you might have to create on at this point.
Luckily enough the app does a good job at sticking to iOS and Android standards, so maybe a general iOS or Android XD kit might be a good place to start.
One resource that can be helpful is the open source UI elements available by Instructure:
instructure-ui : UI libraries made by Instructure Inc. (5.36.0)
Theme Colors and icons:
Hope this helps.
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