Hi there!
Great question! Roman is correct that you're not able to change the tracked URL for an existing Campaign.
That being said, if the only change made to the URL is that it is now https instead of http, our tool should start crawling the https pages without needing to create a new Campaign. You can check to make sure that the https pages are being crawled by heading to your All Crawled Pages section of your Site Crawl and filter by "https://" in the search bar. This can be a quick way to make sure we're capturing that update!
If you're still having trouble with getting those updated pages crawled, feel free to email us at help@moz.com and we can take a look to see what's going on. 

