Hi,
thank you ucho!
I wrote a simply program that capture keyPressEvent, and the code of left soft key is 16777217 that is the code of TAB on my linux desktop!
So is not similar to TAB but is equal to TAB 
I do some other test:
- the soft button used to cancel is mapped on Backspace (event->key 16777219);
- the green soft button is mapped on event->key 16842753
(I don't have any idea which keyboard button is. Perhaps nothing so you can answer at the phone without problems with QT.)
Code:
void MainWindow::keyPressEvent(QKeyEvent* event)
{
input.setNum(event->key(), 10);
ui->textBrowser->append((input));
}
PS: on S60 left sof key is used to open the options menu, is not strange use it to change de focus and not as usual to open menu (like a right mouse click, I know that mouse event are reserved for S60 5th touch screen)?