Hi,

If you need to make changes inside the res.config.settings, lets us explain with an example,

class ResConfigSettings(models.TransientModel):
    _inherit = 'res.config.settings'

    account_no = fields.Char(string='account',
                             config_parameter="module_name.account_no")

then we have to inherit and add it to the view,

<record id="res_config_settings_view_form_inherit" model="ir.ui.view">
    <field name="name">res.config.settings.view.form.</field>
    <field name="model">res.config.settings</field>
    <field name="priority" eval="25" />
    <field name="inherit_id" ref="account.res_config_settings_view_form" />
    <field name="arch" type="xml">
        <xpath expr="//div[@data-key='account']/div[2]" position="after">
            <h2>Test</h2>
            <div class="row mt16 o_settings_container">
                <div class="col-12 col-lg-6 o_setting_box" title="">
                    <div class="o_setting_right_pane">
                        <label for="account_no" />
                        <div class="text-muted">
                            Account No:
                        </div>
                        <div class="content-group">
                            <div class="mt16">
                                <field name="account_no"/>
                            </div>
                        </div>
                    </div>
                </div>
            </div>
        </xpath>
    </field>
</record>

Also you can check this video explaining the same in v12: How To Add Settings/Configuration For Module in Odoo

Thanks