/cb - Opens main GUI window from which you can go to Functions, Robots, or Blocks windows.
/cbf - Opens Functions GUI
/cbr - Opens Robots GUI
/cbb - Opens Blocks GUI - you can get custom blocks here while in any mode creative or survival.
/cbb all - will drop all possible code blocks in stacks of 64 around the player.
Pressing 'C' will open main GUI as well.
While placing any of the group blocks you will notice that all of the choices have numbers next to them. Pressing matching number on keyboard while block selector window is open will instantly place the block in the world.
