Past collection may now be published in the web showroom for internal usage (eg. for sales reps). Buyers will not have access to these published collections, only brand members will have a limited read-only access (order taking being deactivated here).
To publish a past collection,you must have access rights to products module, head to the collections module in your back-office and set the collection status to the new "Closed" status. See the full list of collection statuses in the image below.
This feature is also available in sales catalogs.