On the Global Tools Configuration UI, when setting up a new Node tool version, you have the possibility to install directly from nodejs.org, or setup an install with a zip/tar and add the url of the thing you want to install.
If you go the path of pointing to a specific URL, then it seems you must define a slave filter type, and create a definition for each platform. IE, here's a Windows installer URL, here's a Linux installer URL, etc.
This feature came up because of a current problem with Jenkins global tools updates not running:
Because of this issue on the Jenkins infrastructure, the nodejs tools list is not updating, meaning the nodejs version we want to use is not available for automatic installation.
OK, so, we decide we will mirror the nodejs downloads site, and we would like to create our our reference to our copy. But there seems to be no way to get automatic installation of all versions on all platforms unless using the "Install from nodejs.org" installation type.
So this feature would be to allow you to define your own custom url, where the same structure as available on nodejs.org would be mirrored, and install from there. IE, "Install from URL" where the value is "http://mirror.ourcompany.com/artifacts/nodejs/dist/v8.9.3/"