FenTiger, thanks for the link.............this cleared many doubts
I believe that I've enough of a head start, such that I can order some devices and have a moderate chance of success.
For the benefit of anyone with a passing interest on these devices, I will from time to time, report on my findings.
For starters, I will focus on the IN-34-1, as it is moderately priced and appears to have the most documentation online. I color coded the different cathodes with the function description. This helps to visualize their function and clear some translation mistakes. For instance, there were a pair of "Cathode of the third group", but the magenta-colored one is actually the first cathode.
I also include the device's pinout location.
I am still puzzled by the sentence ".....with the release of the 5th element". I am not sure they are referring to the
5th visual element as indicated by Imo, but perhaps it means the release of the auxiliary cathode.
(Cathode groups 1 thru 3, reset cathode, and auxilliary cathode making the 5th cathode element).
I also believe that I've figured out the overload cathode function, which would should really mean "overflow" cathode.
Sigh...it is a little hard to figure out things without the benefit of a timing diagram.