With Metafields Editor, You are able to modify multiple metafields and modify metafields for additional data types like Customers, Orders, Collections, Pages, Articles, Blogs. If you are on the Basic or Free plan, bulk importing/exporting via CSV files is available as a credit based system. See more details about the csv file format here. If you are on the Pro or Unlimited Plan, bulk importing/exporting can be used with no limitation.
The credit system works like this, you pay an one time fee to purchase some credits. Credits are like minutes in a prepaid plan for wireless phones. Each time you import/export one metafields successfully, one credit is deducted. The app only deduct for successful import/exports. The credit system is useful if you do not have a lot of data to import/export. 10 Dollar give you 1000 credits which is good for 1000 metafields records. If you import 10 metafields for a product, 10 credit will be used.