try to use domain filter in your custom view:

Odoo domain filter 

domain for relational fields 

example:

<field name="my_one2many_field_name" domain="[('some_field', 'in', context.get('allowed_value_list_for_some_field'))]"/>

note: "some_field" used  in example should be available in the same view in xml as normal or as invisible field.

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).