Store the username of the user that last modified the entry

gk_store_who_updated.php

<?php // DO NOT COPY THIS LINE

add_action( 'gravityview/edit_entry/after_update', 'gv_custom_function', 10, 3 );
function gv_custom_function( $form = array(), $entry_id = array(), $object  ){

	$run_on_views = [4049]; //Change this to the IDs of the Views you'd like to run this code 
	$view_id = GravityView_View::getInstance()->getViewId();

	if( !in_array( $view_id, $run_on_views ) ){
	return false;
	} 

	$current_user = wp_get_current_user();
	if ( ! ( $current_user instanceof WP_User ) ) {
		return;
	}

	$field_id_user = 4;	// replace 3 with the ID of the field you want to store the username 
    $update_result = GFAPI::update_entry_field( $entry_id, $field_id_user, $current_user->user_login );	
}