I have a page in one course that I want to LINK to my other courses (so if I edit it, all courses see the latest edits). I DONT want to copy it. Ditto with a file. Or an Announcement. Any object. It doesn't seem like Canvas will allow this (yes, links within a course are allowable).
Generally speaking, linking from one course to another is not recommended. In most cases, students who are enrolled in one course are not also enrolled in the other course. Or, only a handful of students might be enrolled in both courses...not all students. If you link to content from course A to course B ... and students who are enrolled in course A are not enrolled in course B ... then those students would see an error message on their screen because they don't have access to that course.
I hope that will help a bit. Sing out if you have any other questions about this...thanks! Take care, and be well.