The Bulk Editor in Shopify is a simple way of editing many custom fields (and any other metafields) at the same time.
Note, the Shopify Bulk Edit tool does not show Custom Fields by default. You must access the tool through the link in Custom Fields to reveal the fields you created in the app.
WARNING: Bulk editing Custom Fields on Shopify is for experts only! Please be sure that any values you change match the format that each Custom Fields is configured for. For example, an "image" field should be wrapped in a proper image tag. A list of numbers should be separated by the "|" (pipe) character, etc...
This tutorial addresses how to find use the editor in conjunction with the Custom Fields app. See the articles above for how to use the editor itself.
1.) In the Custom Fields App, navigate to the Search tab of Products (Or for the fields you would like to edit).
In this menu, search products you'd like to bulk edit on Shopify.
2.) Open the Bulk Edit on Shopify drop-down menu.
When you access the drop-down, you will be greeted with a Warning message. Make sure you read the warning before continuing.
Custom Fields stores data in a very specific way for each field type. Just follow any patterns you see when viewing the raw data in the bulk editor. Ignoring the data storage patterns will break things and you'll have a bad day! Be careful!
Once finished reading, continue by clicking the I understand the risks. Let's go! button.