Customize ACF WYSIWYG Editor Block Formats

/**
 * Customize block format options in the ACF WYSIWYG editor.
 *
 * This snippet modifies the TinyMCE block format dropdown
 * for Advanced Custom Fields (ACF) WYSIWYG editors by adding
 * custom heading, paragraph, and preformatted text options.
 *
 * Added Formats:
 * - Paragraph
 * - Heading 1–6
 * - Preformatted
 * - Paragraph Big (custom class: p-big)
 *
 */
function sj_customize_acf_wysiwyg_formats( $mce_init, $editor_id ) {

    // Define custom block format options.
    $block_formats = '
        Paragraph=p;
        Heading 1=h1;
        Heading 2=h2;
        Heading 3=h3;
        Heading 4=h4;
        Heading 5=h5;
        Heading 6=h6;
        Preformatted=pre;
        Paragraph Big=p.p-big
    ';

    // Apply custom block formats to the editor.
    $mce_init['block_formats'] = $block_formats;

    return $mce_init;
}

add_filter( 'acf/fields/wysiwyg/toolbars/mce_init', 'sj_customize_acf_wysiwyg_formats', 10, 2 );