Source

File: wp-admin/includes/class-wp-ms-themes-list-table.php

public function column_default( $theme, $column_name ) {
		$stylesheet = $theme->get_stylesheet();

		/**
		 * Fires inside each custom column of the Multisite themes list table.
		 *
		 * @since 3.1.0
		 *
		 * @param string   $column_name Name of the column.
		 * @param string   $stylesheet  Directory name of the theme.
		 * @param WP_Theme $theme       Current WP_Theme object.
		 */
		do_action( 'manage_themes_custom_column', $column_name, $stylesheet, $theme );
	}