Support › General › Custom field in Rank Math title
There is %customfield(field-name)% to display the custom post in the title of Rank Math.
The field is a relation field to a CPT. It displays a number instead of the title of that post.
Is there another way to get the field?
The number is the post ID. You can use the WordPress function get_the_title() to retrieve post title. Or contact RankMath support to run the function on their side.