In the Listener for the add-on, there will be a function that creates the navigation tab. You should be able to ascertain which PHP file handles that by looking at the callback of the aforementioned code event listener, where you changed the process order.
Quite simply there will be a PHP array that defines the tab, title, link etc. also its position. Its position is currently "middle". Change it to "home". That should sit between Home and Forums.
FWIW another valid position is "end" which would sit it after the Members tab.