@EmmaChapman ...
I agree with @SusanNiemeyer that, generally speaking, linking from one course to another is not ideal. However, thank you for also sharing that you have the same set of students in both courses. So, that shouldn't be a problem for your situation. However, just keep in mind that if you copy (import) course content from these courses into future courses and you no longer have the same set of students in both courses, you're going to have to go through any of your content pages to make sure your links have been corrected. Or, if you have other instructors who will be using your content down the road and they do not have the same set of students in each course, this would also be an issue. Just throwing out some potential issues that could arise at this point.
Regarding the accordions... I'm not sure exactly what your course pages look like (and maybe a screenshot or two from you would be useful here), but if you had been using HTML code at one time to design those accordions, I don't think those work any longer...because Instructure had disabled JQuery to make those function. So, people had to come up with other ways to get it to work...as described here:
Solved: Accordion Script Help - Instructure Community (canvaslms.com)
However, if your school has paid for the Cidi Labs / Design Tools product, for example, then you would still be able to design accordion layouts in your course. Maybe you have this? Again, I am not sure what your content looks like, so it's hard to know for sure.
Looking forward to hearing more from you on this...thanks!