In Sales when I go to Product menu I get tree view by default. I did it like this
<record id="product.product_normal_action_sell" model="ir.actions.act_window">
<field name="view_mode">tree,form,kanban</field>
</record>
<record id="product.product_template_action" model="ir.actions.act_window">
<field name="view_mode">tree,form,kanban</field>
<field name="view_id" ref="product.product_template_tree_view"/>
</record>
Same in Purchase and Manufacturing but I have a problem to do the same in Inventory.
This is an original menu that calls an action
<menuitem
action="product.product_template_action_product" id="menu_product_variant_config_stock" name="Products"
parent="stock.menu_stock_inventory_control" sequence="1"/>
how can I make it that when I go to Inventory->Products tree view opens by default
Actually, it's the same. you need to add
<record id="product.product_template_action_product" model="ir.actions.act_window">
<field name="view_mode">tree,form,kanban</field>
</record>
to Product view