Update Picklist values using Workbench

[Chris Piper]

Can admins update multiple picklists per object using Workbench?

[Ryan Brainard]

Do you mean the current value of the picklist or the available items in the picklist? Either way, Workbench can do it, but the method varies. For the former, you can just update the value like any other field, and I should note that it doesn't have to correspond to one available items (e.g. if you have a picklist called Color with items Red, Blue, and Green, you can still set it to Yellow via Workbench). For the latter, you will need to do a Metadata Retrieve of the Custom Object/Field in question, edit the XML locally, and then do a Metadata Deploy. 

As for "multiple picklists," not sure if you mean multiple single-picklists or a Multi-Select Picklist. For the former, just update more than one at a time. For the latter, just delimit the values with semicolons.