There are many ways of doing it.
1) As dunhill has said
2) Same, but with a list of formats.
program:
my_formats = 'Ogg,M3u,M4a,M4b,Mp3,Aac,Ac3,Zip,Rar';
if list_intersection(lowercase($formats), my_formats, ',') then
'Yes'
else
'Nope'
fi
3) Directly display the format
In any case, add new rules in the /preferences/appearance/icons column to add distinctive icons for books, audiobooks, or whatever we save in caliber.
P.S: You can edit your custom column duration or use AudioBook_Duration plugin for that
