You can collect topics whose topic notes contain the text you want.
MultiMaps recognizes instructions you can enable through the macro language operators topicnotestext and topicornotestext.
For example, to collect topics containing text meeting in the notes, type this code in the collection topic notes: topicnotestext:contains:meeting
The Data Collection engine now understands that you want to collect topics contain the text meeting in its notes.
By default, the search is case-insensitive. Apply the casesensitive macro language operator if you want it to recognise the case of letters.
See here for the fastest way to collect topics with the required text in the topic notes.