Hi,

By default, Odoo imports are designed to replace values (especially on many2many fields like tags, BoM components, or storage categories).

    Fields like tags, BoM components, and storage categories are many2many relationships.

    When you import, Odoo sets the field equal to the imported values, which overwrites the existing list.

    That’s why you see old values replaced instead of appended.

You can handle this by first exporting the existing records, editing the exported template, and then re-importing it. This is actually the safest method because when you export, Odoo includes the correct record IDs or external IDs that it uses to link related fields like tags, BoM lines, or storage capacities. Once you have that export, you can simply add the new values you want to append while keeping the existing ones intact. For example, if you want to add new tags to products, export the products with their current tags, then in the same column just add the additional tags without removing the old ones, and re-import. The same approach works for Bill of Materials or storage capacities, you can export the BoM lines or capacity lines, add the new components or capacities as extra rows in the file, and then import it back. This way, instead of replacing the existing values, Odoo will append the new ones while keeping everything else unchanged.

Hope it helps