Navigate to the campaign whose URL you'd like to change, and click "Settings" in the bottom of the left side menu.

By default, you should be on the Campaign Details page. If not, select Campaign Details from the settings page menu.
​
Next, edit the URL field to the new URL of your choosing. Once done, click Save in the bottom left.

Note that we use the campaign URL when checking rankings, running site audits, and providing backlinks data, so any changes to the campaign URL will affect those features.