Glad you found an answer

I've found the best way is to really create it in Polarion and convert it to text as in the video you mentioned

Have you had problems or noticed limitations with the customFields? I haven't been able to properly make a query with a customField (even when creating the filters in Polarion and changing it to a string, only works with normal fields) I've also found that putting more than one customFields in the fields will just return me one of them and not both. Pretty inconsistent all around