pos/pos_to_weight_by_product_uom/views/pos_to_weight.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2017 Grap, OCA   
     License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl). -->

<openerp><data>

        <!-- UNIT OF MEASURE CATEGS -->
        <!-- Form view -->
        <record id="product_uom_categ_form_view_inherit_pos_to_weight_by_product_uom" model="ir.ui.view">
            <field name="model">product.uom.categ</field>
            <field name="inherit_id" ref="product.product_uom_categ_form_view"/>
            <field name="arch" type="xml">
                <field name="name" position="after">
                    <field name="to_weigh" />
                    <button name="action_recompute_to_weigh" string="Set 'to weigh' in each product of this category"  type="object"/>
                </field>
            </field>
        </record>

        <!-- Tree view -->
        <record id="product_uom_categ_tree_view_inherit_pos_to_weight_by_product_uom" model="ir.ui.view">
            <field name="model">product.uom.categ</field>
            <field name="arch" type="xml">
                <tree>
                    <field name="name"/>
                    <field name="to_weigh" />
                </tree>
            </field>
        </record>

        <!-- UNITS OF MEASURE -->
        <!-- Form view -->
        <record id="product_uom_form_view_inherit_pos_to_weight_by_product_uom" model="ir.ui.view">
            <field name="model">product.uom</field>
            <field name="inherit_id" ref="product.product_uom_form_view"/>
            <field name="arch" type="xml">
                <field name="active" position="after">
                    <field name="to_weigh" />
                </field>
            </field>
        </record>

        <!-- Tree view -->
        <record id="product_uom_tree_view_inherit_pos_to_weight_by_product_uom" model="ir.ui.view">
            <field name="model">product.uom</field>
            <field name="inherit_id" ref="product.product_uom_tree_view"/>
            <field name="arch" type="xml">
                <field name="category_id" position="after">
                    <field name="to_weigh" />
                </field>
            </field>
        </record>

</data></openerp>