Instead of modifying existing views in place (by overwriting them), Odoo provides view inheritance where children "extension" views are applied on top of root views, and can add or remove content from their parent.
Code like below->

<record id="idea_category_list2" model="ir.ui.view">
    <field name="name">id.category.list2</field>
    <field name="model">idea.category</field>
    <field name="inherit_id" ref="id_category_list">
    <field name="arch" type="xml">
        <!-- find field description and add the field
             idea_ids after it -->
        <xpath expr="//field[@name='description']" position="after">
          <field name="idea_ids" string="Number of ideas">
        </field></xpath>
    </field>
</field></record>