<?xml version="1.0" encoding="utf-8"?>
<odoo>

<template id="crm_lead_merge_summary_inherit_website" inherit_id="crm.crm_lead_merge_summary">
    <xpath expr="//div[@name='marketing']" position="attributes">
        <attribute name="t-if">lead.campaign_id or lead.medium_id or lead.source_id or lead.visitor_ids</attribute>
    </xpath>

    <xpath expr="//div[@name='marketing']" position="inside">
        <div t-if="lead.visitor_ids">
            Web Visitors: <t t-out="', '.join(lead.visitor_ids.mapped('display_name'))"/>
        </div>
    </xpath>
</template>

</odoo>