We can update every user field (including custom fields) using the Update Existing Users toggle in the Import User screen. However, there is no way to update many users' status from active to inactive or deactivate the users based on a CSV identifying users who need deactivation.
While there is a "bulk deactivation" workflow in the UI, often deactivating users in bulk cannot be done by any single shared attribute. For example, our customers are healthcare provider institutions for which employee turnover tends to be fairly high. Our good customers regularly contact us to inactivate users' as they no longer work for that customer. I should be able to inactivate multiple users via an import process preferrably by having a toggle in the override values to set to deactivate or inactive for the imported update or (less desirable) by including a status column in the import CSV.