Mulesoft doc normally show the latest Mule Runtime docs. However we usually not use the latest runtime version, so its quite inconvenient to find to useful doc.
And this Script will help you to specific the runtime doc version you looking for.
Guide
Install tampermonkey in your browser.
Install the script from greasyfork.org.
Refresh https://docs.mulesoft.com/, and you will see a text input on the page. (Like the image bellow)
Input version and press Enter, doc about Runtime will change to your specific version.
Next time you open this web site it will automatically change the docs version to the one you specific last time.
