Hi,
Well, unfortunately there is no option for that, but you can try a custom code for that.
Try adding this code to the functions.php file in your theme/child theme directory – make sure to have a full server back-up first for safety. For more details you can check the safe coding guidelines.
add_action('wp_footer', 'wp_footer_change_filter_input_placeholder', 9999);
function wp_footer_change_filter_input_placeholder() {
?>
<script>
(function(){
let text = "My placeholder text";
setTimeout(function() {
document.querySelectorAll('fieldset.asp_custom_f input[type=text]').forEach(function(el){
el.placeholder = text;
})
}, 100);
}())
</script>
<?php
}
Change the text variable in the code for the input text you want.