When you define a Many2one field in Odoo, you specify the model (comodel) that the field is related to. However, you don’t directly choose a specific field in the comodel. Instead, the Many2one field stores the ID of the related record in the comodel.

For example, if you have a Many2one field in the account.move model that relates to the account.payment model, this field would store the ID of a specific account.payment record. When you view an account.move record in the Odoo UI, this Many2one field would display the name field of the related account.payment record.

If you want to display a different field from the account.payment model in the UI, you would need to add a related field to the account.move model. A related field in Odoo is a read-only field that uses the values from another field. You could add a related field to account.move that uses the value of the field you want to display from the account.payment model.

Here’s an example of how you might define a Many2one field and a related field in the account.move model:

class AccountMove(models.Model):

    _inherit = 'account.move'

    payment_id = fields.Many2one('account.payment', string='Payment')

    payment_field = fields.Char(related='payment_id.field', string='Payment Field')

In this example, payment_id is a Many2one field that relates to the account.payment model. payment_field is a related field that uses the value of the field field from the account.payment model. Replace 'field' with the name of the field you want to display.

Please note that while you can add these fields in the Odoo UI, you might find it easier to add them in the Python code. If you’re using Odoo Online, you would need to use Odoo Studio to add these fields in the UI.

Best regards,
Maciej Burzymowski