When using canvas on desktop, it is possible to copy the URL of the current page to return to the page later. As far as I am aware, this function is not available on the iOS student app and, I assume, the Android student app. 

While a Canvas URL may not work ideally on the mobile platforms (as it will open a browser page rather than the app), it is very handy for sharing direct links to modules, announcements or assignments in messages or for personal notes and is only possible on desktop currently.

The implementation could be a share icon (pictured below) in the top right corner of each page. Clicking the link would allow the url to the page to be shared to various applications or (am not sure if this is available on Android) allow the 'copy link' option which adds it to the clipboard as plain text. This exact functionality is available in many other apps and is a standard behaviour (on iOS at least).