just in case you didn't solve it yourself.
This can be achieved very easy with form rules:
2. Add two parameters and use this code, where you replace the ParameterField, ParameterValue with yours
document.querySelector("#"+ParameterField.fld +" input").placeholder = ParameterValue;
3. Verify what the console.log line outputs in the developer tools. It may be necessary to modify the ".fld" part in the querySelector line to return "AttText2" or whatevery field you use.
4. Remove the console.log line
Make use of the form rule.