Returns the current "stance" offset for use with the bonus action bar. This value corresponds to what "stance" the player is currently in, and more specifically which set of actions correspond to that stance. Action IDs for special stances start on action bar #7 (or NUM_ACTIONBAR_PAGES + 1), so the offset returned by this function corresponds to the number to be added to NUM_ACTIONBAR_PAGES in calculating action IDs for these action bars.

Note that the UI definition of "stance" includes not just warrior stances but also druid shapeshift forms, rogue/druid stealth, priest shadowform, and various other cases, but does not necessarily include all states normally presented in the default UI's stance/shapeshift bar (notable exclusions are paladin auras and death knight presences).