BuddyPress.org

For each link, you just have to copy the link and give it a distinct name

Assuming you want to list 3 external links:

$link_0 =  "https://www.amazon.com/";
$link_1 =  "https://www.blablabla.com/";
$link_2 =  "https://www.tada.me/";

then for each link, you write the html

<li><a href="<?php echo $link_0; ?>......</li>
<li><a href="<?php echo $link_1; ?>......</li>
<li><a href="<?php echo $link_2; ?>......</li>

And you use the same logic for pages.

Note that if you add many links, you most probably will have to adjust also the nav CSS, to get at least a toggle menu.