I see in the build dated 03-Apr (don't know number yet) the file themes.txt isn't in the Theme folder. This was the file I was able to modify so that the renamed theme appeared correctly under the Theme tag. Has this been "reassigned" to something else?

Part of the localization changes have caused us to replace theme.txt with theme_description.php so that the descriptions can be translated. However, theme.txt will still work, it just is not localizable. You can change to theme_description.php if you want, but it is not needed.