To assign custom breadcrumb values to custom pages, one would usually do something like this in 3.0:

$template->assign_block_vars('navlinks', array(
'FORUM_NAME' => 'test',
'U_VIEW_FORUM' => append_sid("test.php"),
)

However, there is currently no option to replace the "Board index" breadcrumb if the board has a "home page" breadcrumb set up. Also, the 'FORUM_NAME' and 'U_VIEW_FORUM' strings are misleading in terms of a custom page.

It would be very nice to be able to lead your breadcrumb trail from the "home page" rather than the "forum index" link.