The Canvas process works a little different compared to the one we were using for Blackboard.
In Blackboard, the college had to come up with a process that involved always adding an additional Master course and the child sections (the ones you wanted merged) were added into it. This would hide any content created in the child sections from the students (so if you had worked on a child course in-depth, that work would then have to be copied into the Master course after it became available).
In Canvas, when you work through the instructions linked to above, it will have you use the Canvas process (which is applicable for those that have actual Cross-Listed courses they are teaching here at the college, or instructors that are teaching multiple sections of the same course).
The Canvas process will have you adding them together so that one of your sections becomes the primary one (without an additional Master course).
So initially you will have this:
Course1 Course1Enrollments Course2 Course2Enrollments
And after following the Canvas instructions it should look like this:
Course1 Course1Enrollments Course2Enrollments
So whatever you have shown in that primary course (in this case Course1) will continue to be shown after cross-listing.
If you know ahead of time that you will want to have merged / cross-listed courses, then it is best that you go through the instructions above on the Canvas website first and then start creating / copying your content in and just work from the "main" course where all of the enrollments are now falling within.