Add "All Docs" breadcrumb item to user profile breadcrumbs.

all-doc-breadcrumb-item.php

<?php 
function add_all_docs_to_user_directory_breadcrumb( $crumbs ) {
    if ( bp_is_user() ) {
        array_unshift( $crumbs, sprintf( '<a href="%s">All Docs</a>', bp_docs_get_archive_link() ) );
    }
    return $crumbs;
}
add_filter( 'bp_docs_directory_breadcrumb', 'add_all_docs_to_user_directory_breadcrumb' );