Hi @shin
ACF saves the custom fields like the standard custom field feature that comes with WordPress. This means that you should be able to find a plugin that allows you to bulk edit WordPress custom fields and you are good to go.
Searching on Google, I found this plugin: https://wordpress.org/plugins/custom-field-bulk-editor/screenshots/, but I haven’t tested it yet. You should be able to find importer plugins that have this kind of feature too.
You can also add the feature yourself if you want. Kindly check this page to learn more about it: https://nodedesk.zendesk.com/hc/en-us/articles/202330901-How-do-I-add-custom-fields-to-my-bulk-quick-edit-page-.
I hope this helps 🙂
