you can have more than one buttonscroller per window (at least i can't see anything preventing this).
there is 6 animations for controls:
windowopen
windowclose
visible
hidden
focus
unfocus
there is 2 animations for windows:
windowopen
windowclose
in addition, there is an extra one for controls available as a shortcut:
visiblechange
this just defines the visible animation in the usual manner, but automatically generates a new hidden animation as the reverse of the visible animation.
eg:
<animation effect="slide" start="100,0" time="100">visiblechange</animation>
is equivalent to:
<animation effect="slide" start="100,0" time="100">visible</animation>
<animation effect="slide" end="100,0" time="100">hidden</animation>
it should be all in the online manual
cheers,
jonathan