From the documentation it seems that I need to enter "delete the id number of the flow", however, it's not obvious where I enter the command. Not in the terminal window it seems.
I can delete individual nodes by selecting each one but I now have two flows displayed, one being empty.
Thank you wb666greene and knolleary for your replies. I did look at the hamburger but, for some reason, didn't notice the flows/delete entry. It's pretty obvious, once you know how.