Save time managing your picklists. You can now delete, activate, deactivate, or replace multiple custom picklist field values at once. Previously, you modified them one at a time. This feature is available only for custom picklists with predefined values. This feature is generally available.
Where: This change applies to Lightning Experience and Salesforce Classic in all editions.
How: Go to the custom field definition page for the picklist field. In the Values and Inactive Values sections, there’s a checkbox next to each picklist value. You can select multiple values and use one of the new buttons: Delete Selected, Deactivate Selected, Replace Selected, or Activate Selected.
Bulk Manage Picklist Values (Generally Available) (salesforce.com)