Currently the built-in QR-code generator only supports one short line of text. Some QR-codes require multiple lines (separated by \n or \r\n) e.g. for a standard SEPA SCT on invoices to facilitate payment. I suggest to allow \r and \n in the input text and process accordingly. And a larger input field width would be nice.
Ah, turns out we already have this request; thanks for filing - this shows that the request indeed is important. *** This bug has been marked as a duplicate of bug 128718 ***