Let's say we want to draw the transition graph of a Turing Machine that accepts that language L and then write the sequence of moves done by the TM when the input sequence is $w = abbcbba$ so I had some thoughts on how this could be built.
$q0 - q1: a,a,R$
$q2 (loop): b,b,R$
But then I'm getting stuck here, I could see $b,b,R$ to the final state and then add a separate node to account for the case $m=3$, but I'm teaching this to myself so maybe someone can step in here and get me back on track.
This might work: