I think the issue here is not if one can change CV’s on a Marklin msd3 on any full blown digital system such as NCE, ECOS, CS3, Massoth etc, it’s the fact that Cabcontrol isn’t able to! And I believe the person that commented on the ESU forum is correct that the Cabcontrol just isn’t capable of handling the change because the electronics/hardware doesn’t allow it to go over a certain voltage because it thinks that it’s going to break the locomotive in the programming track, so it shuts the system down. CanControl primarily is an item geared for smaller scale. The extra voltage for the converter was just added to make sure it’s G scale compatible but I doubt they did a full blown test on how it works in real life using Gscale.
I’d really would like Alec from ESU to comment on this issue (he has said that Cabcontrol reads dcc so all LGB trains have that priority so msd3 isn’t really the issue) because I’m sure he or ESU doesn’t know the answer, they haven’t tested it! But I might be wrong and that would be a pleasant surprise. Cabcontrol is a nice setup especially for beginners like me, but if your only able to run 1 train on the track it gets boring real quick! ECOS would be a good step up, but with lack/extremely slow response from their team on emails I just switched to the competitor.
I’m on CS3 right now and am actually liking the setup, so far am able to run 3 trains, and am sure it can handle more.
Andrew