Re: how to edit menus?
The navigation menu is in the header.php starting here https://trac.buddypress.org/browser/tags/220.127.116.11/bp-themes/bp-default/header.php#L46
You can change the links by creating a Child Theme so your revisions won’t be overwritten when BP is upgraded.
You won’t find the BP menus in the Appearance > Menu unless you revise the links in navigation menu an code navigation menus function in your theme’s functions.php file and add the template tag for that in header.php – https://codex.wordpress.org/Navigation_Menus
You can also try out this plugin – https://buddypress.org/community/groups/add-all-nav-links-to-bp-adminbar/home/