odoo-event-addons/event_website_hidden/views/event_event.xml

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

  <record id="view_event_form_inherit_event_website_indexed" model="ir.ui.view">
    <field name="name">event.event.view.form.inherit</field>
    <field name="model">event.event</field>
    <field name="inherit_id" ref="event.view_event_form" />
    <field name="arch" type="xml">
      <field name="tag_ids" position="after">
        <field name="website_indexed" widget="boolean_toggle" groups="event.group_event_manager" />
      </field>
      <!-- <div name="button_box" position="before">
        <widget name="web_ribbon" title="Hidden on website" bg_color="bg-warning"
          attrs="{'invisible': [('website_indexed', '=', True)]}" />
      </div> -->
    </field>
  </record>

</odoo>