EA is a tool that you can use for almost everything – even for UI. But one important note – EA is not a GUI Builder – it is a modelling tool. That means that you get the model of your UI and whatever your code-generator (hopefully it is a machine and not a user) generates out of your model becomes the GUI.
My entry point is Win32 User Interface modelling – but this is not an indicator for the target platform (the outcome only depends on that what your code generator creates out of that model).
Very often people ask especially for the Tab Control and why it is not possible to switch the Tabs: Here is the answer: because within a model you should see everything what is in the model and you typically should not hide some controls on a different Tab.
So the visualisation of a Tab Control is only a picture – a placeholder for a Tab Control. If you want to model the Tab Pages – here one valid approach: add to the Tab Control within the diagram another UI diagram (right mouse button|Add|Add diagram|User Interface – Win32|User Interface – Win32), then define the Tab Control as composite (right mouse button|Advanced|Make composite) – then double click on the Tab Control and define the Pages, one by one – I personally prefer Group Box as container.
For my code generator I create the Tab Pages from Top to Down (meaning the first Group Box becomes part of Tab Page 1, the second part of Tab Page 2, and so on).
Of course this is just one option of many and I would be happy to hear about your approaches.
For doing all the event handling stuff –> use signals and activitiy diagrams, simulate it with AMUSE and some nice Mockups (hopefully Rizo will read this and provide a nice link showing that cool stuff as a video).