How to implement custom type

[SPlatten]

I want to implement a new Text class based on the existing Text class but with added functionality, events and properties. Is there a good tutorial that will demonstrate exactly how I can do this ?

[JoeCFD]

Create a new xml file as NewText.qml and use the existing Text in it like
ExistingText {
...
}

[Bob64]

What @JoeCFD said is what I have done to customise some built-in QML components but it depends whether everything that needs doing can be done at the QML level. For example, if extensions are needed at the underlying C++ level there is not really any support to do this. Probably you would need to copy the source of QQuickText to a new class and add the extensions to it.