I sometimes use the challenge tags to see if I've done something for a certain prompt and tend to combine with my creator tag to narrow down especially during amnesty when I have the spreadsheet to work from too becuase I still haven't come up with an offline system for tracking my fills that works well for me. A few things I've tried don't quite work and using the tags helps.

The tags limit on a premium paid account is 2000 tags, I don't know if you've looked into that option or not. Just a suggestion, in case it's a viable option for the comm, especially with the tagging.