Hey @SusanFuschetto!
Before getting started, I have a disclaimer: Please remember students have the ability to turn course notifications off if they do not want to receive them. Therefore, even if course notifications are sent, students with notifications turned off will not receive them. If notifications are an important part of your course, I would suggest relaying that information to your students and asking them to at least turn on specific notifications for your course. Whether they do or not is up to them.
How do I manage notifications for a single course?
When content is imported into a new course, a copy of that content is created and added to the new course. This new copy in the new course is no longer connected to the original course. Therefore, if edits are made to the content in the original course, it should not affect the newly imported content in the new course. Likewise, if the content is edited in the new course, it should not affect the content in the original course.
When editing an announcement and the Send button is selected, notifications should be sent out to students in the specific course you are editing. It should not matter if the announcement was initially created in that course or if it was imported from another course.
If there is a date and time added to the Available from field to delay the posting of the announcement, an email notification should be sent at the date and time the announcement becomes available.
Hope this helps!