Yes Possible, all you need is the following

Step 1: In the Object: AiCollaborationActivityLine

define _rec_name = 'country_id'  -- this set Name property for your custom object, which will be easier to perform default search.

Step 2: In the Object Hr.Employee.

Search View (XML) add field for collaborations_ids == Thus user can search directly

Same kind of features are also available in standard objects like Stock-Picking, Invoice -- Do refer for more ideas

Dear deep, thank you very much!

I also just received another solution variant sent by Jorge Tuñez:

<record id="ai_rh_gedic_studies_search" model="ir.ui.view">
        <field name="name">ai.rh.gedic.studies.search</field>
        <field name="model">hr.employee</field>
        <field name="inherit_id" ref="hr.view_employee_filter"/>
        <field name="arch" type="xml">
            <xpath expr="//search" position="inside">
                <field name="collaborations_ids" string="Activity of collaboration" filter_domain="[('collaborations_ids.country_id.name','ilike',self)]">
                </field>
            </xpath>

        </field>
</record>