Q.removing old sections of stumps from newer bush
In NW Ohio. Have quite a few over 17-20 yr old rose of Sharon bushes, some of which the main trunk portion has died out but a newer bush has grown in next to it. Almost looks like one larger trunk that split off. Any way I’m looking to remove the older trunk portion to below ground level without damaging the newer one. Is this possible?

If you dig around the old dead trunk to make sure you're not cutting into any live roots or pieces of trunk, you should be able to saw the dead trunk out without any problem. Here's an article on pruning rose of sharon: https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/pruning-rose-of-sharon.htm