(depreciated)
The Theme Visibility Manager adds granular administrative control over which themes are visible in the themes menu for any given site. Themes can be made hidden or visible on a blog by blog basis (through the themes menu) or on a site-wide basis through the ‘Theme Visibility Manager’ page in the Super Admin menu.
Themes can be active even if they are invisible, but this can only be controlled by Super Admins. Blog administrators only have control over visible themes.