{cate parent_id="{$page:parent_id}"}

{cate:loop}
• [cate:name]
{if:OW.int("[cate:children]")>0} {cate2 parent_id="[cate:cate_id]"}
{cate2:loop}
• [cate2:name]
{/cate2:loop}
{/cate2} {/if} {/cate:loop}

{/cate}