Issue #2712835 by Leksat: Plain text field default value is not translatable

core/config/schema/core.data_types.schema.yml

@@ -487,7 +487,7 @@ field.value.string:
   label: 'Default value'
   mapping:
     value:
-      type: string
+      type: label
       label: 'Value'
 
 # Schema for the configuration of the  String (long) field type.