Temur,
thanks for your time. Sadly even if without syntax errors the filter is not working at all and shows all the products:
<field name="product_id" on_change="onchange_product_id(parent.pricelist_id,product_id,qty,parent.partner_id)" domain="[('pos_categ_id', 'in', context.get('category2'))]"/>
Just a note: product_id is a many2one field, not a one2many, and pos_categ_id (char) is related on pos_categ_id on product,template (many2one).
Here is my xml:
<?xml version="1.0"?>
<form string="Workcenter2 Orders">
<header>
<field name="state" widget="statusbar" statusbar_visible="draft,paid,done" statusbar_colors="{"cancel":"red"}"/>
</header>
<sheet>
<group col="4" colspan="4">
<field name="name"/>
<field name="date_order"/>
<field name="session_id" required="1"/>
<field name="partner_id" on_change="onchange_partner_id(partner_id, context)" domain="[('customer', '=', True)]" context="{'search_default_customer':1}"/>
</group>
<notebook colspan="4">
<page string="Products">
<field name="lines" colspan="4" nolabel="1">
<tree string="Order lines" editable="bottom">
<field name="qty" on_change="onchange_qty(product_id, discount, qty, price_unit, context)" attrs="{'invisible':[('pos_categ_id','=','pos2')]}"/>
<field name="product_id" on_change="onchange_product_id(parent.pricelist_id,product_id,qty,parent.partner_id)" attrs="{'invisible':[('pos_categ_id','=','pos2')]}"/>
<field name="price_unit" invisible="1"/>
<field name="pos_categ_id" attrs="{'invisible':[('pos_categ_id','=','pos2')]}"/>
</tree>
</field>
<div class="oe_clear"/>
<div class="col-xs-12 text-center">
<button name="622" string="Update" class="oe_highlight" type="action" attrs="{'invisible':[('x_kot_order','=','Ready')]}" />
</div>
</page>
</notebook>
</sheet>
</form>
And this is what the order looks like when I hide the 'pos2' category (the empty line in the middle).