I have just released G4P V4.3.9 and it should be available in the Contributions Manager in a day or two.
In this release most G4P controls now support simple tool tips that appear when the mouse moves over the control, disappearing after a set time or when the mouse moves off the control, whichever happens first.
Adding a tool tip to a control requires just a single statement but for more advanced programmers it is possible to create custom tool tips in the Processing IDE. This video shows tool tips in action and the library examples include the sketches used in the demo.
G4P source code reference