The 'import' attrs is valid according to the rng definition of the list view. It is used in a few views in Odoo. However, it didn't actually work (in most cases, it worked by chance because it is set to "0" in addition to create="0", and create="0" already disables the import feature). With this ref, the 'import' attrs is taken into account and we can now disable the import feature even if the create one is enabled. Moreover, it is now documented.