Exclude Blocks from the Block Based Widgets Editor

Hello there,

You can use PHP code to register the block, then check if the current page is the widget page and return $meta_boxes variable at that point. For example:

// Register a hero content block for Gutenberg.
add_filter( 'rwmb_meta_boxes', function( $meta_boxes ) {
    global $pagenow;
    if ( $pagenow == 'widgets.php' ) {
        return $meta_boxes;
    }

    $meta_boxes[] = [
        'title' => 'Hero Area',
        'id'    => 'hero-area',
        'type'  => 'block', // Important.
        ...
    ];
    return $meta_boxes;
} );

Follow the WordPress documentation https://codex.wordpress.org/Global_Variables#Admin_Globals