flectra/addons/mail/views/ir_actions_views.xml

<?xml version="1.0" encoding="utf-8"?>
<flectra>
    <data>

        <record model="ir.ui.view" id="view_server_action_form_template">
            <field name="name">ir.actions.server.form</field>
            <field name="model">ir.actions.server</field>
            <field name="inherit_id" ref="base.view_server_action_form"/>
            <field name="arch" type="xml">
                <field name="link_field_id" position="after">
                    <field name="partner_ids" widget="many2many_tags"
                        attrs="{'invisible': [('state', '!=', 'followers')]}"/>
                    <field name="channel_ids" widget="many2many_tags"
                        attrs="{'invisible': [('state', '!=', 'followers')]}"/>
                    <field name="template_id"
                        attrs="{'invisible': [('state', '!=', 'email')],
                                'required': [('state', '=', 'email')]}"/>
                </field>
            </field>
        </record>

    </data>
</flectra>