Setting to update only blank fields

[arnelap]

for example for UTM_source, utm_campaign, etc. via hidden fields.
if later on, the subscriber completes a second MC4WP form I don’t want the subscriber’s initial source data to be overwritten with newer UTM data.

In my plugin, I see there are only two ways to configure the update process:

• Update existing subscriber: YES
• Update existing subscriber: NO

I like to add the ability to "Update only blank fields”.

https://secure.helpscout.net/conversation/661110620/15308?folderId=253120