Hi @lxb41 ...
I am a little confused by your "folder" terminology, but I think I know what you are getting at (Canvas doesn't call courses "folders"). Let's say that you have two courses for the Fall 2025 semester in Canvas (Course A and Course B). Both of these courses have the same content, but the only real difference is the student enrollments. Assuming that we cross-list these two courses together, let's say that Course A is our "parent" course and Course B is the "child" course. We'll cross-list the "child" course into the "parent" course so that all enrollments (both students and instructors) from Course B get added into Course A.
All students/instructors from Course A and Course B would only see Course A when they log in to Canvas, and this is the course they would access (even though some originally enrolled in Course B). You, as the instructor, would also only see Course A, and you would not see Course B. You would only make updates to your course content in Course A.
As I had mentioned in my initial reply, you would be able to see the enrollments for both courses in your "People" page of Course A. As far as content is concerned, yes, since students are now cross-listed together in Course A, they will see any of the content that you load into the course. This would include things that you've mentioned like the Syllabus, Quizzes, Readings, Links to Resources, etc.
I'm hoping I covered everything you asked about, but if you still have questions/concerns, please reply back. Thanks!