Currently, when copying a course, only the "main"/"everyone else" due date for each assignment is copied, and any differentiated due dates are lost. This may make sense when assigning differentiated due dates to specific students, since they're probably not in the copied version of the course (How do I assign an assignment to an individual student?). (I would actually prefer to see these copied as "empty" differentiated due dates that I could then place the next year's students in as needed as well, but that's less important than the main issue below)
However, I have a course with two different "tracks" in it that I keep organized by section. Students can be either in the "regular" track and complete one set of lessons and assignments or the "accelerated" track that has additional more advanced lessons and assignments interwoven with the regular coursework. I use section-specific due dates for basically every assignment in the course to pull this off (How do I assign an assignment to an individual student?), and right now this means I have to go in and edit the section-specific due dates on every single assignment every year because they do not copy (I keep a paper list of what goes when for that track and spend several hours clicking on everything to get it rescheduled).
I would like to see an option to preserve section-specific due dates on course copy for situations like this where the different section-specific due dates are part of the course structure rather than a one-off situation that will be different the next time the course is run. I'm envisioning this as a new checkbox on the course copy page (near where the option to adjust due dates is) that says something like "also copy due dates for [name] section" for each section in the original course.