I'm adding new pages beneath the Admin page itself (using Admin > Page Management). None of them are showing up in the listing when viewing the Admin page (the Console module, it seems).

 I added pages beneath the Host page, and they show up in the listing when viewing Host.

How are new "admin" pages supposed to show up in that listing? Is it automatic?

Huh. I must have set just the right bad combo of settings or perhaps something got stuck.

I deleted both test pages from the Recycle Bin (since it wasn't going to let me remake a page w/ the same name otherwise).

I made a new page beneath Admin. Admins had permission to edit, as well as Intranet Admins that I'm pulling from Active Directory.
All other roles left unchecked.

Updated, and the page showed up in the Admin console. No other changes thereafter make it go away. (I twiddled "Allow Indexing", set the other roles to explicitly denied, added another role from Active Directory [all permissions unchecked].)

Well, thank you Sebastian!