I ended up with this solution in functions.php
, thanks to the offical WordPress documentation at: https://codex.wordpress.org/Rewrite_API/add_rewrite_rule
First added a custom rewrite rule like so:
function custom_rewrite_rule() {
add_rewrite_rule(
'^agenda/([^/]*)/([^/]*)/?',
'index.php?page_id=10&agenda_id=$matches[1]&agenda_name=$matches[2]',
'top' );
}
add_action( 'init', 'custom_rewrite_rule', 10, 0 );
Then this needed to be added:
function prefix_register_query_var( $vars ) {
$vars[] = 'agenda_id';
$vars[] = 'agenda_name';
return $vars;
}
add_filter( 'query_vars', 'prefix_register_query_var' );
Now URL’s such as /agenda/1/event-title work like a charm! And passes the variables needed.
PS: Remember to save the permalinks settings in the backend once again, or this code won’t work!