Customize output of AMAZON.QnAIntent

Hi! Currently I am building a Lex bot that makes use of AMAZON.QnAIntent. The knowledge base is a Kendra index. I understand that there are two attributes x-amz-lex:qnA-search-response and x-amz-lex:qnA-search-response-source that I can use in order to customize the fulfillment answer of the bot, for example:

"((x-amz-lex:qnA-search-response)) Source: ((x-amz-lex:qnA-search-response-source))"

However I cant customize the sources and it always display them as comma separated, even if there is only one source (source1,). Is there a way to customize this?

Also, is there a way to add newlines to the fulfilment? for example: "((x-amz-lex:qnA-search-response)) \nSource: ((x-amz-lex:qnA-search-response-source))"