Bernie,
I'm not a pro but I read a lot of manuals ;-)
Your Yamaha and most of the better arrangers have a "left hold" or "lower hold" that will sustain your LH notes when you lift your hand from the keys. It does give some chord changes a much smoother sound when you have to reposition your whole hand.

Another way to achieve this is to program one of the unused accompaniment tracks to sound a sustained triad in strings, organ, choir, etc. Typically this accompaniment track would continue to sound when you release the chord to use the bender, etc.

I notice that Roland's recent BK's have a lot of flexibility when it comes to how each track interacts with the sustain pedal.
My $.02,
Ted