An Atari 8-bit version of this game exists, it is also mentioned on this site at the Imagic 1-2-3 shovelware entry, then why isn't listed here between the platforms?

By the way, how do I add a platform to an existing game entry? There are also other entries on this site that miss a few platforms.

When you want to add a new port (platform) for existing game entry, use left menu: Contribute -> New Platform

However this game was only released for Atari 8bit in that compilation you mentioned. Our current database structure means we don't add ports that didn't have own separate release. Yes, many of us don't like the result, there should be some indication of this game being on compilation for another system. For the time being, you can add such info as trivia.