Changing Custom Fields Data
If it is simply your goal to change the data in a custom field, and have it apply to all the relevant contacts, you can take the following actions:
1. Run an Advanced Search on your custom field.
2. "Select All" to export these contacts. Your custom fields will export too.
3. In the csv file, remove the unnecessary fields or change your custom field entry to whatever you desire.
4. Re-import the file into Nimble, and select "Override existing contact fields with data in the CSV".
Now all your contacts with the custom field will set to the new values you created in your csv file.