WordPress File wp-includes/class-wp-editor.php

mce_buttons

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

mce_buttons_2

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

mce_buttons_3

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

mce_buttons_4

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

mce_css

Filters the comma-delimited list of stylesheets to load in TinyMCE.

media_buttons

Fires after the default media button(s) are displayed.