Enrich Product Feeds With Shopify Metafields

Yes, you can bulk edit metafields in the Shopify admin itself. The app will update and push the metafield values and specifications to Google Merchant Center. You can also select and customize specific product metafields that you wish to push.

A metafield stores a single piece of custom data on a product or variant, such as a GTIN or color. A metaobject stores reusable structured content made up of multiple fields that you can reference across many products.
In the app you enable metaobjects under Settings, Product Customization, Metaobject, then map each field of the metaobject to a Google Merchant Center attribute. Only metaobjects that are referenced in a metafield within your Shopify admin are available for selection.

Three Google attributes expect a true or false value passed as a boolean type metafield. These are adult, identifier exists, and isBundle.
When any of these need to be set, create the metafield definition as a boolean type rather than text so the value syncs correctly.

String type metafields work for a wide set of attributes including title, description, brand, color, google product category, GTIN, item group id, material, MPN, pattern, multipack, age group, availability, condition, and gender.
Select the string data type when creating the definition for any of these.

Each attribute expects a specific format and the format is case sensitive. If a value does not follow the expected format, the data may not push to Google Merchant Center.
For example, availability accepts only in_stock, out_of_stock, preorder, or backorder, and price expects a number followed by a currency such as 15.00 USD. Always match the value to the format listed for that attribute before syncing.

The app follows a fixed priority order. Customizations made inside the app take precedence, then metafields, then metaobjects, then the default Shopify value.
The order is Customization, then Metafields, then Metaobject, then Shopify Value. This means a value you customize directly in the app will always override a metafield or metaobject value for the same attribute.