The chromatic button accordion is a mystery to most musicians. Its keyboard looks like a jumble of buttons that don't seem to be in any useful arrangement.
In this case, reality is the opposite of the perception. They right hand button layout is logical and easier than the keyboard of a piano accordion. It is played in fingering pattern. There are patterns for the scales. To change from one key to another, just move the hand a little but keep playing in the same pattern. There's no keeping track of sharps and flats as with a piano keyboard. The button keys all fall into place in the pattern. There is some redundance in the keyboard so there is more than one way to finger a scale. And no matter what key is being played, the accidentals will all fall into the same place in the pattern.
The chromatic accordion plays the same note on both the push and the pull, just like a piano accordion. The bass side will have one of the systems used on piano accordions, most typically the Stradella, but there is some variation.
There are two commonly-used layouts for the chromatic accordion, the B-system and the C-system.
The notes are arranged in minor thirds along the length of the keyboard, and in half-steps going across on the diagonal. The B system has the B-flat notes in the inner row, and the note sequence runs out and to the right. The C system has the C notes in the outer row, and the note sequence runs in and to the right.
This seems to be the instrument of the future for the very serious accordionists. Young people are choosing them for competitions, and I have heard them described as being more finger friendly than piano accordions.