Teac GVI - Manual (Page 46)

46
SHOW/HIDE SUB-CHANNELS
Because a stacked instrument can contain many sub-channels, it may be
useful to collapse a stacked instrument so that only the Main MIDI Mixer
channel is visible. The black arrow to the left of the Stacked Instrument
channel field is a toggle switch that shows or hides the sub-channels.
In the screenshot above, the upper view shows the sub-channels (notice the
arrow points downward) and the lower view hides the sub-channels (notice
the arrow points to the right).