How do I change the ‘Complete testimonial by ‘ link title text

In your theme’s functions.php file, add similar code as follows.

add_filter( 'twp_link_title_text', function() { return 'More by '; } );

or

function my_content_more() {
return 'More by ';
}

add_filter( 'twp_link_title_text', 'my_content_more' );