Dear John,
thank you so very much for answering and answering so soon! You just gave me a hint. I see that the "BEACON LIGHT SET" Requires a Parameter. I didn't put anything there in the parameter line yet. I will try this first prior going into the other optional solutions you recommend.
So, my perception of a missing BEACON ON and BEACON OFF wasn't that wrong then. Thank you for keeping track of it. I just couldn't understand if it was a problem with MSFS or the simconnect, as you say.
Basically my request is not for a specific aircraft model. I had the same issue back then with FSX as well. Some addons require proper light setting and you had no chance to verify if everything was set correctly because some models didn't have the red light beacon switch "depicted" in their 2D or 3D panels. I managed to install some default 2D panels as addon panels into some aircrafts, but I didn't like that solution either. I have my external hardware Switchboard that connects via USB, it works like a game controller. I prefer using this for all aircrafts, disregard appearance / simulation of the switch itself in the 3D cockpit.
I will come back here and let you know if I managed with the Parameter setting 0 or 1... maybe thats also the cause for some other similar issues I had. I did not understand the "Parameter" - but its obvious... 0 is off, 1 is on... just a different way to address those "flags" or binary information.
until next time,
OE-PKR over and out,