WordPress at a glance
filter is not described

mce_buttons_2 filter-hook . WP 2.0.0

Filters the second-row list of TinyMCE buttons (Visual tab).

Usage

add_filter( 'mce_buttons_2', 'filter_function_name_1344', 10, 2 );
function filter_function_name_1344( $buttons, $editor_id ){
	// filter...

	return $buttons;
}
$buttons(array)
Second-row list of buttons.
$editor_id(string)
Unique editor identifier, e.g. 'content'.

Where the hook is called

_WP_Editors::editor_settings()
mce_buttons_2
wp_tinymce_inline_scripts()
mce_buttons_2
wp-includes/class-wp-editor.php 608
$mce_buttons_2 = apply_filters( 'mce_buttons_2', $mce_buttons_2, $editor_id );
wp-includes/script-loader.php 670
$toolbar2 = apply_filters( 'mce_buttons_2', $toolbar2, 'classic-block' );

Where the hook is used (in WP core)

Does not used.