Custom fields editable also in cart

-- HikaShop version -- : 2.3.5
-- Joomla version -- : 3.3.6
-- PHP version -- : 5.4.27
-- Browser(s) name and version -- : Firefox 34.0
-- Error-message(debug-mod must be tuned on) -- : Custom fields editable also in cart

I have created some Custom fields for Products
During selecting Options for the product everything is OK
all fields are editable.

But my customers wants also to correct some Options later during Checkout in the Cart-Display
screenshot: Custom-fields-in-the-cart.jpg

so my question:
which PHP-files do i have to change (customize) for this special issue
For this special Project i have already made some changes in the Views:
(only the duplicates in my template)

templates\my-template\html\com_hikashop\product\show_block_custom_item.php
templates\my-template\html\com_hikashop\checkout\cart.php

I have created some Custom fields for Products
During selecting Options for the product everything is OK, all fields are editable.

But my customers wants also to correct some Options later during Checkout in the Cart-Display
screenshot:

so my question:
which PHP-files do i have to change (customize) for this special issue
For this special Project i have already made some changes in the Views:
(only the duplicates in my template)

templates\my-template\html\com_hikashop\product\show_block_custom_item.php
templates\my-template\html\com_hikashop\checkout\cart.php

Can i use the php-code from show_block_custom_item.php also in the cart.php ?

Thank you for your help!