Over time, you will inevitably discover that you have keywords in your Personal Knowbase data file that are not assigned to any articles. Perhaps you’ve deleted the articles that they were originally assigned to. Or you created keywords you intended to use, but your needs changed.
Of course, there are valid reasons to keep some unassigned keywords. There may be keywords you aren’t currently using, but may need again in the future. Or you may want to keep complete sets of keywords for fixed groups like months or days of the week. Or you may want a keyword for each member of your club, even if no articles yet pertain to some members.