I've wrestled with this problem before and sent a question to the forum, but, for various reasons, I'm learning very slowly about how to deal with the relatively old digital components I've invested in. So, I apologize to anyone who comes across this question and has the feeling that he's seen this issue before--and then wonders, "Why can't this guy get it?"
I have a relatively simple question: Can I change the address on a loco that came with a digital starter set (the address is 72, which was "factory set") with the limited components I currently have without investing $100 or more in a 6021 Central Control Unit?
Since I have stuck myself with a 6023 Central Control, I'm limited to four loco addresses: 10, 20, 30, 40. If I can't manipulate one of my two locos to one of those four addresses, the 6023 Central Control is, it seems to me, essentially useless. (I wasn't planning on using the interface capability for the foreseeable future). I plan to use the Control 80 for the other loco. As things stand now, the Control 80 is doing fine at controlling either loco; meanwhile, I can't get the 6023 to do much of anything.
Also, I'd like to verify that I WILL be able to change loco addresses with a 6021.
Thank you for any insights on this problem.

Paul24

The other thing to check, especially if it is an older start set, is the decoder itself - it might have dip switches..

To r/mark, Adrian, and Tom:
Thank you all very much for the suggestions. I really appreciate your donating your experience. It gives me a better grasp about the whole digital system I'm dealing with. This is what I understand is going on: (1) My 6023 is a bit of an albatross assuming I don't use its interface capability; (2) I could solve my problem pretty simply if I could just find a local Marklin user who could change my loco's address for me; this sounds to me like the cheapest, most sensible solution; (3) getting a mobile station might make sense—I'll look into it—but that sounds as though I'll be abandoning all the recently purchased components and all the time I've invested in trying to understand how they work.
I suppose I could sell the old stuff on eBay and try to recoup some of my investment if I opted for a mobile station, but something tells me I'll just be forced to spend more money on mobile-station-related components. However, I understand that updating to MFX might give me and my grandson literally more bells and whistles to play with.
Regarding the Control 80's ability to change addresses. I tried it, but I had no luck. This doesn't mean I did the steps correctly, however. It would be helpful to find out definitely whether it was even possible with a Control 80.

Paul