You can edit the JSON in another application. Be warned that your changes are not validated!
The Course Search tab lists all courses for the coming semester. Click on the + button to add a course. Each section is listed separately, so make sure to get all the ones you want. You can click on a course to see more information about it in the upper-right panel.
On the right-hand column, you can click and drag courses to reorder them. The ones at the top are given the highest scheduling priority. From here, you can also remove courses, star them, and disable them.
The Schedule tab is, of course, the main event. Scheduling is simple: first, all of your starred courses are scheduled, regardless of conflicts. Then, as many remaining courses as possible are scheduled as long as they don't conflict: the algorithm starts from the top of your list and goes down. Courses that are disabled, however, won't be considered. So, to change your schedule, just use reordering, starring, and disabling, rather than paging through multiple schedules.
Hyperschedule was created by Radon Rosborough and friends during Fall 2017 registration.