How are you interested in changing it?
Depending on what changes you are looking for, you may be able to do it via adding code to your child theme’s functions.php file or (if you aren’t using a child theme or prefer using a plugin) the Code Snippets plugin. For instance, here’s an option to add an “Underline” button and here’s another modification:
// Add underline and outdent/indent option to TinyMCE fields
add_filter( 'submit_job_form_wp_editor_args', 'customize_editor_toolbar' );
function customize_editor_toolbar( $args ) {
$args['tinymce']['toolbar1'] = 'bold,italic,underline,|,bullist,numlist,|,outdent,indent,|,link,unlink,|,undo,redo';
return $args;
}