This is a simple Design Mode extension that demonstrates new capabilities regarding inspecting, and supporting, different mode types/role access in Webflow Designer.
In your terminal, change to this directory and run webflow extension serve. Don't have the Webflow CLI? Follow the directions here: https://developers.webflow.com/cli/reference/webflow-cli
At Webflow, create a new app in your organization settings under "Apps & Integrations / Develop." The name doesn't really matter, but "DE Mode Tester" is fine. Use a dummy description and URL. In "Building blocks", toggle on the Designer API.
Go to your site, hit E to open applications, and find "DE Mode Tester". Select it, and use "Launch development App".
This should run the app being served from your local machine.