I submitted a ticket.
Megan Walsh suggested to use the Leonardo board in the Arduino IDE, but it does not work with the w26 codeBit. She wrote "The codeBit was designed for use with the Code Kit app so it may not work or be buggy with the Arduino IDE. I believe what you are trying to do may be theoretically possible. However, we do not intend for the codeBit to interface with the Arduino IDE."
It is very disappointing to be stuck with the Code Kit app, which is very limited. I was expecting more from littleBits. They do not seem to be interested in opening the codeBit to the Arduino IDE.