In pcshortc.txt, the chord shortcuts BIAB has predefined are listed. This includes the following line:

;sus2@2 add2@2 m+@m#5 dim7@dim 7aug@7+ sus4@sus 11@9sus 9sus4@9sus

Are both sus2 and add2 defined as 2? (PG Music: commas are totally cool. Please consider using them in future documents. Thanks.)

Bob

Yes, and there is Xadd9, which is also converted in BIAB to X2.

Are both sus2 and add2 defined as 2?

Yes, both get converted to the 2 chord. The 2 chord is treated differently, in some styles C2 is C D E G, and on others it is C D G (ie no 3rd). Ideally we would have had 2 separate chords, C add 9, and C2. But for now, we just have the one.