Hi,

In Odoo, when multiple modules are modifying the same field, the order of inheritance and execution matters. In your case, you want to customize the domain of the sale_line_id field in the helpdesk.ticket model, which has already been modified by the helpdesk_sale_timesheet module.

To achieve your goal, you can use a technique called field re-declaration. This technique allows you to redefine a field in a way that incorporates changes from other modules while adding your own modifications. Here's how you can do it:

1. Create a new module or use an existing one.
2. In your module, inherit the helpdesk.ticket model.
3. Redefine the sale_line_id field, including the changes you want to make to the domain.

Here's an example of how your Python code might look:

from odoo import models, fields

class HelpdeskTicketInherit(models.Model):
    _inherit = 'helpdesk.ticket'

    # Redefine the sale_line_id field with your custom domain
    sale_line_id = fields.Many2one(domain="[('your_custom_domain_here')]")

By doing this, your module's changes to the sale_line_id field will take precedence over those made by the helpdesk_sale_timesheet module, and your custom domain will be applied.

Remember to replace 'your_custom_domain_here' with the actual domain expression you want to use.

This approach ensures that your changes are applied without directly modifying the field defined in the helpdesk_sale_timesheet module, thus avoiding conflicts and maintaining compatibility with other modules.

Hope it helps