Yes, but keep in mind that any changes you make to the actual courses associated with a curriculum will show up for all actively enrolled learners. If you remove a course from the curriculum, the course will be automatically removed from the profiles for all associated learners (assuming the learners don’t have the course in question assigned under another curriculum as well).
If you add a course to an existing curriculum, you will be prompted to set the New Course Initial Due Date. This is a one-time only operation for you to indicate when the course should be due for all learners actively enrolled in the curriculum. By default, this date will be set to the current date plus the rollover (or 365 days from the current date, if you’re working with a non-recurring curriculum). Trainings in recurring fixed curricula are always due on the same date and so the field is not required for those curricula.
Learners enrolled in the curriculum after you make any change will have their due dates set by using the offset field.
Learners who have already completed all trainings within a non-recurring curriculum will not be required to take new trainings since they are no longer considered "actively enrolled."
Deleting a course will simply remove it from the users My Learning page under the applicable Curriculum title. This just removes the assignment, not any course completions. Any prior course completions will still remain on the users' transcripts.
If you update a course, the updates automatically push out to all learners enrolled in the course. In other words, if you add a new section to a course, or change an exam question, the LMS will automatically ensure that all enrolled learners see that new section or question so you would not have to do anything at the Curriculum level.
If you change a course so extensively that you need to create a new course shell (in other words, you’re using a different course code than you were for the original training) you should use either the course swap or course add functions.