How do I undo a course import without affecting what I already have for this year?
You might not like this answer, but I don't know of a good way. We had an issue like this a few months ago where someone imported a course from Commons into all of their courses by accident. The only way to "undo" it was to go into each course and manually delete what had been imported.
I suggest contacting support right away to see if they have any other options. Click the Help button on the left side of Canvas and if you have phone or chat available, use that. Otherwise use the Report a Problem link to ask.
If you do need to remove things manually, some items will have dates which should help. Pages and Files list dates they were added. Other items, those may take a little bit more work to clean up.
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