Append values to existing custom fields

[kushh23]

What problem does this address?

Users cannot append values to custom fields in existing posts; they can only overwrite them.

What is your proposed solution?

Implement a feature that allows appending values to custom fields instead of overriding them during the import process.

Feature Summary

Enable the ability to append data to existing custom field values when importing posts.

Reported by : https://secure.helpscout.net/conversation/3134830329/475903