misc: maintain block prefilling data with references to row index (#75162)

wcs/forms/root.py

@@ -472,6 +472,9 @@ class FormPage(Directory, TempfileDirectoryMixin, FormTemplateMixin):
             prefilled = False
             locked = False
 
+            if block:
+                field_key = f'{block.id}${block_idx}${field_key}'
+
             if field.get_prefill_configuration():
                 prefill_user = get_request().user
                 if get_request().is_in_backoffice():