Odoo-Build/snippets/mail.message_activity_assigned.set_access_link_my_activities.xml

<data inherit_id="mail.message_activity_assigned" priority="50">
    <xpath expr="//p[1]" position="replace">
        <p style="margin: 16px 0px 16px 0px;">
            <t t-if="activity.res_model == 'hr.employee'">
                <a href="/web?debug=1#action=365&amp;model=mail.activity&amp;view_type=kanban&amp;cids=1&amp;menu_id=1" style="background-color:#875A7B; padding: 8px 16px 8px 16px; text-decoration: none; color: #fff; border-radius: 5px;">
          My Activities
        </a>
            </t>
            <t t-else="">
                <a t-att-href="access_link" t-att-data-oe-model="activity.res_model" t-att-data-oe-id="activity.res_id" style="background-color:#875A7B; padding: 8px 16px 8px 16px; text-decoration: none; color: #fff; border-radius: 5px;">
          View <t t-esc="model_description or 'document'"/>
        </a>
            </t>
        </p>
    </xpath>
</data>