Browsers ship with their own developer tools. These are amazing tools to help you debug your web application. Consider learning how to use them.
Once you have your local installation of DEV running, you can attach to either the Chrome or Edge Debugger.
If you do not see your editor here, consider contributing to the documentation. 😉
Preact has their own developer tools in the form of a browser extension. These tools are currently supported for Preact version 10.x and up.
DEV currently uses Preact 8.x so the Preact developer tools are not an option, however Preact 8.x+ is compatible with the React developer tools extension which is available for Chrome and Firefox.