Specific Syntax in a Flow

So I have a flow, and I want to set the value of an external variable be a string that includes a value returned by a Server Connect that has just run in the flow.

Here is the run part of my flow:

run: {
   action: "{{user_message.setValue('This event is currently being edited by NAME so is being opened for you in read-only mode.')}}"
     }

I want to replace NAME with the value of:

sc_lock_event.data.returned_values.text_value

What syntax within the run action will allow me to do this?

(I’ve tried various options in the user interface and not found a way to make it create the text-value-text combination I am looking for)

Best wishes,
Antony.