You can add new custom fields to your list at any time, up to a limit of 40.
How to add custom fields
Head to the Lists page and choose ‘Edit’ from the dropdown menu. You can do this even if your list is in use i.e. there is a campaign pending to send to it.
Click ‘Add new custom field’
This will add a row for a new custom field
Enter a name and select a type for your field. The name must be unique to the list and can’t contain any spaces. As you type the name, a drop-down will appear containing matching names of existing custom fields. You can choose to select one of these or carry on typing something different to create a new field name.
When you’ve finished adding fields, click Save to save the changes to your list. You’ll be asked to confirm this since you can’t change the type of a field once added. Also if your list is in use, you won’t be able to change the name once saved while the list has ‘in use’ status.
If your list is in use
Your list is in use if it’s associated with a pending Campaign, Automation or Journey. Editing existing custom fields or the list name is not permitted in this state to protect the integrity of your deliveries. For this reason, you’ll see the field names and their data type but you won’t be able to edit them.
Example of the edit list screen for a list that is in use
You can however, add a new custom field to a list that is in use.