To rewrite a URL using the Dashboard, you can use the same values are defined in the API Definition options, just set them in the endpoint designer instead for your path.
Step 1: Add an endpoint for the path
Browse to the endpoint designer in your API and add an endpoint that matches the path you want to rewrite.
Step 2: Configure the URL rewrite
Add the regex capture groups and the new URL to the relevant sections.
Step 3: Save the API
Press the save or create buttons to save the changes and make the URL rewrite active.