I’ve been exploring blues, which for many years was the absolute weakest area for me, because there is nothing farther away from what I played as a kid and what I studied. My teachers only taught very traditional piano music, music which is to this very day described as “classical music”, although that term is highly misleading and terribly vague.
Three are missing for a complete chromatic scale – Db, Eb and Ab.
All the scales I used are essentially Dorian, but with a blues note added that we normally call “b5”. I picked the three easiest keys for Dorian: D Dorian, G Dorian and A Dorian minor. Those add Bb and F# to the seven white keys. Three are missing for a complete chromatic scale – Db, Eb and Ab. But I added them with Abm7 (Ab and Eb) and Bbm7 (Db).
In a way what I wrote ends up being fully chromatic in a very sneaky manner.
I tried to keep this reasonably simple, for teaching purposes. However, I slipped in bVIm7 and bVm7 around the Vm7 chord before slipping to IVm7, and anything that truly sounds good is never really simple because of the harmonic and interpretive demands of creative music.