what is [tab button] ? how it works ? and how to add it?
I have tested the tab button feature with the latest 6.50 release and it is working fine.
The Tab Button state holds the "Down State" (highlighted) of the button that is the current selection whilst all other buttons are in their "Normal State".
Of course for this to be seen working your buttons must have at least these two distinguishing states (I.E: Colours)