In 3270 mode, the BackTab() action emulates the BackTab (⇤) key on the 3270 keyboard. If the cursor is already in a modifiable field but not in the leftmost position, it moves to the leftmost position. Otherwise, it moves to the leftmost position of the first modifiable field to the left of the cursor position, wrapping to the previous line and around from the top to the bottom of the screen if necessary.
In NVT mode, it does nothing.
|3270||Shift-Tab||Ctrl-a + Tab||Shift-Tab||Shift-Tab|