To do this, we will not modify the Bibtex file, but rather create an auxiliary file where we will associate categories and comments to a number of the references. For instance, if we want to associate the category "Topological Recursion" and the comment "This article..." to the article whose Bibtex key is "cer12", we will add the following text in the auxiliary file:
\ArticleLabel{cer12}Why would we want to have such categories and comments? Categories are particularly useful if they match some classification of the articles, whether as files in a computer, or as physical printouts. If you keep articles in a number of folders, the program will enable you to find in which folder a given article is, and to list the articles in a given folder. As for comments, keeping them in a centralized file is safer than having them as annotations (handwritten or electronic) on a copy of an article, which might well get lost.
\ArticleCategory{Topological Recursion}
This article ...