I think I'm starting to figure this out. I traced the voltmeter wires, which led back to the Master Switch. That wire (red) is linked to the second fuse, which appears to be the bridge between the Master Switch and the 4 linked circuit fuses.
Here is the Green (purple on the original) and red wire on the Master Switch.
I have them tied together but need some female-dual male connectors for connecting these and the cabin lights.
There are two leads that can be attached to a common bus bar for the black (common ground) leads. One comes from the 4 fused circuit group and one from the Master Switch and fuse combination. Since I'm not wiring a speedo ATM, I'm using those open switches to add a bilge pump and switched power socket (cigarette lighter type) under the voltmeter and next to the distribution panel. I am also considering wiring a second power socket over the chart table and providing power for a chart plotter that is going to be mounted over the chart-table. I am using a Fuji Q552 w/wireless GPU and Raster Charts. This way, I can take the Q552 out of its mounts and use it in the cockpit.
That looks to be the only modifications to the wiring and distribution panel ATM. I'm building into the Distribution network from the battery-regulator-fuse-Switch to the distribution panel so that a second panel would not be hard to add. That would allow for additional circuits as needed, if extra equipment, instruments or systems are added to the boat. I would probably keep them fused and just put the additional panel under this one on the Port Side Aft. The radio, will have a direct take-off from the battery, fused in-line. That should do it for now.
Work left to be done on the electrical is the tracing of all the existing wires and running the additional wires so I can close up the coach-roof. I would like to mount a battery and add a charger/shore plug fitting, so I can keep a battery charged and have working bilge pumps. I'll need wiring and coax for the mast. I'm putting an antenna, 360 white LED masthead light and wind vane up there. A windex light to illuminate the wind vane on the same circuit as the masthead light would be a nice comfort feature for night sailing.
While I have a soldering station set-up, I'm going to add the red and black leads with blade connections but they will be attached to the existing wires with an in-line butt connection/shrink wrap connection. That way, the panel can come completely out for modification if needed. I'm running mostly 14 gauge wire, with 16 g for the lighting. The radio power line will probably get 12 gauge running in the coach roof conduit by itself. I would like a radio that I can operate remotely from a plug in the cockpit. Wiring for that will probably need to be routed in the coach roof as well.