eclipse - how to extend the build-in javascript libraries?

Question

While modifing my eclipse juno 4.2 with some WebDev-Features, I am currently stuck while adding library support for JQuery, JQMobi and other.

This is my situation:

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This would be my goal:

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The Problem

Is it only possible to manipulate the build-in JS-Libraries of Eclipse through plugins or manually too?

Because, when I click on Add JavaScript library , I don't get this:

In my case, there is only User Library - how can I add other ones?!

These links were kind of helpful, but don't show a solution to my problem:

https://stackoverflow.com/a/12892508/1370465

http://www.ibm.com/developerworks/library/os-eclipse-jsdt/

http://marketplace.eclipse.org/content/jsdt-jquery#.UVB0clfAm2U

Answer 1

A user library represent sets of JavaScript files chosen by a user and preset through the User Libraries preference page.

Everything else is provided by plug-ins.