Discovered an undoc feature "data-input-preset-prefix-input"... added to API as "prefixInput"

modules/backend/assets/js/october.inputpreset.js

@@ -10,6 +10,8 @@
  *   for the source and destination input elements.
  * - data-input-preset-type: specifies the conversion type. Supported values are:
  *   url, file, slug, camel.
+ * - data-input-preset-prefix-input: optional, prefixes the converted value with the value found
+ *   in the supplied input element using a CSS selector.
  *
  * Example: <input type="text" id="name" value=""/>
  *          <input type="text"

modules/backend/classes/FormField.php

@@ -458,6 +458,10 @@ class FormField
             'data-input-preset-closest-parent' => 'form'
         ];
 
+        if ($prefixInput = array_get($this->preset, 'prefixInput')) {
+            $newAttributes['data-input-preset-prefix-input'] = $prefixInput;
+        }
+
         $attributes = $attributes + $newAttributes;
         return $attributes;
     }