Was the authorized center you mentioned, also the dealer you bought the boat from? If so, and maybe regardless, if the repair facility can't fix the problem, they should have escalated to Grady corporate.
One concern now is that you did work on the boat and that can complicate the issue..
So if you want to find the problem on your own and you are somewhat handy with electrical diagnostics, you don't need a voltmeter per se. You need a clip on amp probe. It also is a digital voltmeter but if you have an excessive parasitic drain, you need amperage readings.
Assuming that your current drain is one of the loads, your first steps are to measure the parasitic drain , confirm it is excessive ( it should be quite low) and then disconnect all loads to confirm that the drain has returned to normal. Then you reconnect loads one at a time (but turned OFF) and see when the drain jumps up. I am not sure what the trim tab relationship is but I would look at that later.
Can you confirm that the drain and run down batteries occurs when the boat is not being used and doesn't happen when the boat is being used.
Skunkboat has some good info on his post. Follow those also.
He also asked what position you leave the battery switches when docked overnight. That is important info to know.
Finally, have you added any additional equipment to the boat that is powered directly off of the batterie
As for the CL7. It is made by Garmin. the power cable from the Garmin (depending on model) may fit the CL7.
Since you know the Garmin works, if you plug in the CL7 to that cable and it doesn't work then the CL7 is broken.
It may be under warranty from Yamaha?
If it works, you have a connection problem.
As for the trim tabs. they say they have power. that can be misread if they are connecting the meter to a ground point that is good and measuring the positive 12V feed. It is possible the negative side (ground) of the trim is not connected. Its very hard to troubleshoot something like this over text.
The CL7, trim and Battery may be related or may have absolutely nothing to do with each other.
Part of the troubleshooting scheme needs to be isolating the CL7 and the Trim by pulling their fuses or otherwise disconnecting them.
Then troubleshoot the batteries/charging problem.
At the batterries, look for directly connected devices like the bigle pump(s).. usually brown with red stripe wire. Verify that the Dash switches and float switches operate the pumps and that they are not stuck on. I have seen pumps jammed but not blow a fuse.
If there is a "Memory" feed and fuse at the battery, remove the fuse. Often it is a red&pink wire.
Is there anything else, besides the Battery Switch, connected directly to a positive post of a battery?
Thanks for all your great ideas. The boat is still at the shop so I plan to share this information with the techs tomorrow morning. I’ll let you know what they say. Thanks again!!