As the title: is there a way to navigate between posts of the same subcategory using the
next_post_link functions? But maintaining however both the category and the sub-category of the post.
If you’ll take a look at
next_post_link Codex page, you’ll see it’s usage:
<?php next_post_link( $format, $link, $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' );
As you can see, third param is
in_same_term and it’s default value is false. If you set it to true, then the function will return next post from same category. (If you want the term from different taxonomy, you can change fifth param).
So answering your question... Yes, there is a way to achieve this. It can look like so:
<?php next_post_link( '%link »', '%title', true ); ?>