It can be changed within index.php using the theme editor in the dashboard. You just have to search for the following codes;
wp_list_categories('show_count=0&title_li=&depth=1');
and add the “hide_empty” parameter to the list. Just put after depth=1 the &hide_empty=0
To make it look like this;
wp_list_categories('show_count=0&title_li=&depth=1&hide_empty=0');
How to display All Categories in the main page
This is what I want to do but the index php is empty
You need to edit it on your PC as the right index.php file will not be displayed in the WP admin editor.