Store custom checkout pane data to order
I found a solution. With my custom field called &quot;Test me&quot; and machine name &quot;field_test_me&quot; created in my Order Type entity I could save the data from Custom Checkout Pane with $this-&gt;order-&gt;set() function instead of $this-&gt;order-&gt;setData(). Of course I needed to change $this-&gt;order-&gt;getData() to $this-&gt;order-&gt;get() everywhere where used.
I don't understand what's the difference between set() and setData(), but it seems to store my Custom Checkout Pane values to my custom fields created in my Order type entity.