It seems from the documentation that your tool is scriptable (Harmony Script) using a component of Qt called QtScript that is built into your tool. Scripting of things that do not need a complex user-interface should be achievable using only a text editor (as in the one-line example on the Harmony Script Interface Documentation page you linked), a working understanding of ECMASCript (aka JavaScript, not the same as Java, see ECMAScript Reference) and maybe reference to the Qt documentation (for an understanding of signals/slots and class member information).

If you need a complex UI then Harmony Script provides access to Qt's UI tools through its UILoader class. The *.ui files UILoader ingests can be constructed using the Qt Designer tool. You will get a Qt Designer program with the install of a Qt SDK, in your case I'd go with Qt 4.8.7: here. You might also download the current Qt Creator which can provide a full IDE for Qt development, including Designer in embedded form.