BuddyPress.org

Documentation for this is in bp-core-buddybar.php

Some working examples for navigation (since 2.6) here.

And here a working example for:

1. remove Delete Account on user profile settings tab
2. add a new sub-nav item for “Memberships” to Profile > Settings

1 )

function bpex_remove_profile_settings_sub_tab() {   
	// remove Delete Account from Profile Settings
	bp_core_remove_subnav_item( BP_SETTINGS_SLUG, 'delete-account' );
}
add_action( 'bp_actions', 'bpex_remove_profile_settings_sub_tab' );

2 )

function bpex_add_sub_nav_to_profile_settings() {
global $bp;
$parent_slug = 'settings';
$child_slug = 'memberships';
		
		//Add subnav item 	 
		bp_core_new_subnav_item( array( 
			'name'			=> __( 'My Memberships', 'textdomain' ),
			'slug'			=> $child_slug, 
			'parent_url'		=> $bp->loggedin_user->domain . $parent_slug.'/', 
			'parent_slug'		=> $parent_slug, 
			'screen_function'	=> 'bpex_profile_membership_screen'
		) );
}

		function bpex_profile_membership_screen() {	
			add_action( 'bp_template_content', 'bpex_profile_membership_screen_content' );
			bp_core_load_template( apply_filters( 'bp_core_template_plugin', 'members/single/plugins' ) );
		}

		function bpex_profile_membership_screen_content() {
			do_action( 'my_membership_post' );
		}
add_action( 'bp_setup_nav', 'bpex_add_sub_nav_to_profile_settings', 100 );

function bpex_membership_stuff() {
echo 'Some stuff here ?'; ?>
<h2>Lorem Ipsum for ever !</h2>
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<?php
}
add_action( 'my_membership_post', 'bpex_membership_stuff' );

Add this to bp-custom.php