In order to include a list of categories within the “article_read” GTM tag, you should consider adding a new key-value pair to this tag. The new key could be named as “article_categories”. The value of this key would be an array or list of the relevant categories for each article. These categories could be strings like “Electricity”, “Refrigeration”, “Sanitation”, “Water & Sewer”, “Ventilation” and “Heat”. So with this addition, when your GTM tag “article_read” is triggered, it would not only contain your standard keys like “news_id” and “article_title” but also an “article_categories” list that contains all the relevant categories of that particular article. This approach would offer the flexibility to associate zero, one or multiple categories with each news article.