The list management itself is entirely broken. Addresses can be added both under List properties and in the address book itself, but the two are not in sync. Addresses that appear in List properties are authoritative; those in the address book itself are not. There appears to be no relationship between the two or any reason why a list is simply not a free standing entity.
Simple things, like double clicking an address book with a list, will both expand the tree node and open the address book properties window. What’s more, why is a list a child node at all in the address book tree listing? It seems to serve no purpose whatsoever.
Adding entries to list properties — the authoritative source — when they already exist in the address book results in duplicate entires, until you click another address book and then return, removing the duplicates. Why?
Oh, lovely, now clicking on list child displays the list of active list email addresses. How entirely unintuitive, that it took an hour to deduce how this works. It was empty before, even with addresses added.
Very disturbing.
Also discovered Yahoo Mail disables inactive accounts. What a terrible service.