To customize the single member header

member-header.php

/yourtheme/buddypress/members/single/member-header.php

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<?php

$wcv_profile_id = bp_displayed_user_id();
$wcv_profile_info = get_userdata( bp_displayed_user_id() );
$wcv_profile_role = implode( $wcv_profile_info->roles );


//$vendor_id   = get_the_author_meta( 'user_login' );
if ( $wcv_profile_role == "vendor" ) {
    $vendor_name_message = get_the_author_meta( 'user_login' );
    $current_user = wp_get_current_user();

    echo "<br><br>";
        if ( is_user_logged_in() ) {
            echo do_shortcode( '[button link="/members/'.$current_user->user_login.'/messages/compose/?r='.$wcv_profile_info->user_login.'"]SEND ME A PRIVATE MESSAGE[/button]' );
        } else {
            echo do_shortcode( '[button link="/my-account/"]LOGIN TO SEND ME A PRIVATE MESSAGE[/button]' );
        };
    echo do_shortcode( '[button link="/members/'.$wcv_profile_info->user_login.'"]VIEW MY PROFILE[/button]' );
    echo do_shortcode( '[button link="/vendors/'.$wcv_profile_info->user_login.'"]VISIT MY STORE[/button]' );

}

?>