This is not possible I’m afraid since how would the websocket server know what to listen to. Both the client and the server have to have the same URL and, unlike web servers, it isn’t possible for the server to serve a wildcard. In fact, I don’t think that would work well with real-time comms anyway.
There would be some potential workarounds you could do with something like Socket.IO that lets you create channels (rooms).
However, you might not need what you think. This is because each client that connects to the socket gets its own unique ID. So it is easy enough in Node-RED to process clients independently. In fact, this is the default. Try connecting several clients with each sending a different message and arrange the input messages to be sent back out again. You will find that each client only receives its own messages. In order to broadcast an input message, you have to remove the client ID from it.