This is the buddypress menu and you'll have to use the buddypress function to add new item there.
You can use bp_core_new_nav_item() function to add the new menu item.
Use the bp_setup_nav hook to add the item.
For example:
add_action('bp_setup_nav','my_custom_menu_item');
function my_custom_menu_item(){
$slug = 'custom';
bp_core_new_nav_item( array(
'name' => __('My custom', 'vibe' ),
'slug' => $slug ,
'position' => 99,
'screen_function' => '',
'default_subnav_slug' => '',
'show_for_displayed_user' => bp_is_my_profile(),
'default_subnav_slug'=> ''
) );
}
For more information on bp_core_new_nav_item() function, refer:
https://codex.buddypress.org/developer/function-examples/core/bp_core_new_nav_item/