WordPress: How to Remove a Category From Menu Lists
The list of categories that is most often displayed in WordPress comes from the Categories widget (Appearance > Widgets). Unfortunately, the widget does not allow you to drop a particular category or categories from the list. This is easily done by editing the functions.php file found in your child theme in the wp-content/themes directory. If the child theme does not have a functions.php file, copy it from the main theme and put it in the child theme’s directory. To drop a category from the list add this:
/*The following function excludes a category from the right-side menu widget. */
$exclude = “140”; // The IDs of the excluding categories
$args[“exclude”] = $exclude;
to the functions.php file betfore the end of php tag (?>). The example excludes category 140. To determine the category number go to Posts > Categories and open the category you want for editing. You will see something like “tag_ID=140” in the URL for that page. That’s the category number.
If you want to exclude several categories, separate the numbers with a comma, e.g. “1,5,140”