Hi

Try the following method,

Inherit the Existing Search View

You’ll need to locate the original search view, usually named something like view_report_pos_order_filter.

Then, inherit it and add a custom filter for product_categ_id like this:

<record id="view_report_pos_order_filter_inherit" model="ir.ui.view">

    <field name="name">report.pos.order.filter.inherit</field>

    <field name="model">report.pos.order</field>

    <field name="inherit_id" ref="point_of_sale.view_report_pos_order_filter"/>

    <field name="arch" type="xml">

        <xpath expr="//filter[@name='product']" position="after">

            <filter name="product_categ" string="Product Category"

                    context="{'group_by': 'product_categ_id'}"/>

        </xpath>

    </field>

</record>

Hope it helps