But, it also looks like you need to spend some time in the civilauto help file.....The AeccSettingsObjectLayers Object is covered pretty well (as well as the current docs do, anyway).
Ah, I see it now. I actually have spent an awful lot of time in that help file, mainly because it is so bad that everything is a puzzle that must be "figured out"...
This is one of the many things that is missing from the overall graphic of the Object Model. If you look at the graphic containing the class hierarchy, it gets down to the "Settings" object off of the "Document" and "Database" classes, but then it ends without showing any of the Settings content. And the "Settings" item is one of the many broken links, so clicking on it yields an error. It's easy to find it once you know its there, and it's possible to find it if you just start reading through all the class descriptions, but it's very difficult to find otherwise.
I'm now discovering the roundabout way that it's necessary to use this document, and now that I'm getting the hang of it, I'm finding more things hidden in it. It is incredibly difficult to use, though. Autodesk seriously needs to create a Civil-3D SDK with complete documentation that can be loaded into the IDE, like the ObjectARX one. One that has some EXAMPLES, and tells you things like the Item() methods are implemented using the array syntax in C#...
Or is it just unreasonable to expect a good API for a product that is barely-functional for the daily tasks of its average users...?