Adding placeholder text to form fields is one of the ways to explain to customers what should they fill. In this tutorial, we'll walk you through detailed steps on how to add placeholder text to form fields in Blue Form Builder, a simple and powerful Magento 2 form builder extension.
https://www.magezon.com/magento-2-form-builder.html

1. Open the edit page of a certain form, then open Magezon Blue Form Builder tab to open the builder interface.
2. Hover over an element then click Edit to open its settings.
3. Open Advanced tab and you'll find Placeholder field where you can enter placeholder text.

That's all you need to do. Just follow these easy steps to add placeholder text to your form fields.