Filters the list of statuses which can be applied to an order using the “Status” select menu when editing or adding a new order. Passes an array of statuses.

apply_filters( "pmpro_order_statuses", array $statuses );

Parameters

$statuses

array

Source

File: https://github.com/strangerstudios/paid-memberships-pro/blob/master/adminpages/orders.php