The request is a little bit old, but I have made a mod for 1.7 implementing a action button for setting ticket as answered.
in include\staff\ticket-view.inc.php search for
<a id="ticket-print" class="action-button"
insert BEFORE this line
<?php
if(!$ticket->isAnswered()) {?>
<a id="action-answered" class="action-button" href="tickets.php?id=<?php echo $ticket->getId(); ?>&a=process&do=answered">Mark answered</a>
<?php
}?>
in scp\tickets.php search for
$inc = 'tickets.inc.php';
if($ticket) {
add below
if($_REQUEST=='process' && $_REQUEST=='answered')
{
$dept = $ticket->getDept();
if(!$dept || !in_array($dept->id,$thisstaff->getDepts())) {
$errors='Access denied. Ask admin to get permissions to mark tickets answered';
} elseif($ticket->markAnswered()) {
$msg='Ticket marked answered';
} else {
$errors='Error marking ticket as answered';
}
}