For Froms:
At the button of the form, you have a space for Buttons having the property IButton.isProcessButton() == true
:
I am not sure you can something else in this area. The grid for the fields (and for the buttons not set as process buttons) is in an other area. Here a screenshot (with the layout debugger):

The Table has the properties:
The Test button is not a process button.
The OK and Cancel buttons are process button
For Pages:
For pages, the situation is a little bit different, you can use IPage.setPagePopulateStatus(IProcessingStatus)
to set a status line. This will be interpreted by the form containing the content of the page and added at the bottom of the form.

Here some examples:
@Override
protected void execPageActivated() throws ProcessingException {
setPagePopulateStatus(new ProcessingStatus("Activated: " + new java.util.Date(), IStatus.INFO));
}
or:
@Override
protected void execPageDataLoaded() throws ProcessingException {
setPagePopulateStatus(new ProcessingStatus("Loaded: " + new java.util.Date(), IStatus.WARNING));
}
And this one for table pages:
@Override
protected void execPageDataLoaded() throws ProcessingException {
setPagePopulateStatus(new ProcessingStatus("Data loaded: " + new java.util.Date(), IStatus.INFO));
}
Of course, like for each text displayed in the UI, it would be better to use TEXTS.get(..)
instead of String directly.