Yes there is a trick to set the default value of a notification node:
Enable the "Accept raw HTML/JavaScript input in msg.payload to format popup", and then use a JavasSript setTimeout fucntion to set the input value.
See this flow example:
[{"id":"f914f79421306774","type":"function","z":"6bd860295ce77e37","name":"payload to dialog input","func":"let newPayloadStr = \n \"<script>setTimeout(function(){$('.md-dialog-container').find('input').val('\"+\n msg.payload\n +\"')},100)</script>\";\nmsg.payload = newPayloadStr;\nreturn msg;\n","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":640,"y":320,"wires":[["7ae014a7ea05f37e"]]},{"id":"7ae014a7ea05f37e","type":"ui_toast","z":"6bd860295ce77e37","position":"prompt","displayTime":"3","highlight":"","sendall":true,"outputs":1,"ok":"OK","cancel":"Cancel","raw":true,"className":"","topic":"","name":"Allow Javascript","x":840,"y":320,"wires":[[]]},{"id":"e8f04e18e5457365","type":"inject","z":"6bd860295ce77e37","name":"","props":[{"p":"topic","vt":"str"},{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"Test","payload":"my value","payloadType":"str","x":450,"y":320,"wires":[["f914f79421306774"]]}]
