Using butler in Trello, when someone is added to a card, I want to look up a specific card and copy a custom field value from that found card to the newly created card.
Trello help gives the example of looking up a native field such as {carddescription} on the found card {foundcarddescription}, and that custom fields are ((%customfieldname}} but it appears you can't combine the two ideas ((found%customfieldname}} doesn't work, nor {foundcustomfieldname}
What is the correct format to use the value in a custom field of a found card?