You can easily restore courses if you need to use them again.
To restore an archived course, head to Training > Courses and filter for Archived Courses. Then click Manage Course under the course you want to restore.
Under Edit Course in the side menu bar, select Unarchive Course.
Please note that the progress of the users that were enrolled in this course before archiving it will appear as it was before the archival. However, the course will not be restored as part of the curricula that it was a part of before archiving it.