Hi,

You can hide the default “New” button and replace it with your own button that opens the wizard.

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

    <field name="name">project.project.tree.inherit</field>

    <field name="model">project.project</field>

    <field name="inherit_id" ref="project.view_project_tree"/>

    <field name="arch" type="xml">

        <!-- Hide default "New" button -->

        <xpath expr="//tree" position="attributes">

            <attribute name="create">false</attribute>

        </xpath>

        <!-- Add custom button to trigger wizard -->

        <xpath expr="//tree" position="after">

            <header>

                <button name="%(your_wizard_action)d"

                        type="action"

                        string="New"

                        class="oe_highlight"/>

            </header>

        </xpath>

    </field>

</record>

Hope it helps.