The sequence field was removed from pricelist items because it did not control which pricing rule was applied. This reduces confusion for users by making the interface better reflect how Odoo actually selects pricelist rules.

Task  : https://www.odoo.com/web#id=33672&view_type=form&model=project.task&action=327&menu_id=4720

Pad : https://pad.odoo.com/p/r.02caf3c3e92184ab0dc7b9cdc6518980