Custom Form Labels
You can customize the label of any form field on the Contact Form element. This will allow you to customize the placeholder text that appears on the form.
However, this will not overwrite the label shown in the Analytics or the field names in integrations.
Using the Text Answer Element
If you would like to collect data for a custom field in an integration, or have the correct question text shown in the Analytics, you can create a custom field that blends in with the Contact Form, using a Text Answer (Short Answer or Long Answer) element:
Drag and drop the Text Answer element in the contact form (in this example we used the Short Answer element) and activate the option/setting: "Use Question as Placeholder":
In the Analytics, default fields from the Contact Form element can be retrieved in the "Personal Data" section. However, note that the data gathered by the Text Answer element is displayed in the "Responses" section: