I'm guessing it's not a bug, since none of them (I have 9) have an operant TOC panel. More likely a FaIthlife clearly defined policy (clause visualization assumes users should already know books included).
I don't use visualization that much, and for the NT, and OT, no big deal ... I know the abbreviations, etc.
But when it comes to the Deuterocanon:
(1) not sure what books were included; trial and error, and
(2) what abbreviations to use (don't have them memorized)