I'm trying to modify expense report ( view_hr_expense_sheet_form ). There is a table at the bottom in which users can add expenses but also include previously created expenses that weren't send to the manger yet - I don't want that.

User should only be permitted to add completely new records, without ability to choose existing expenses.

This is how this field is declared inside Odoo:

    nolabel="1" 
    widget="many2many" 
    domain="[('state', '=', 'draft'), ('employee_id', '=', employee_id), ('company_id', '=', company_id)]" 
    options="{'reload_on_button': True}" 
    context="{'form_view_ref' : 'hr_expense.hr_expense_view_form_without_header', 'default_company_id': company_id, 'default_employee_id': employee_id}">                                                                  
            
...

How can I archive this?

Other option would be, to only show records that are not assigned to any other existing sheet if that way it would be easier.