There are a few different parts to this graph.
You have the graph itself. You are on your way there already since have figured out how to plot two (or more) pens on the one chart. I would back off the update rate. Every 5 minutes for 24 hours is simply too many points to cleanly show the data. Try every 15 minutes for 24 hours.
If that is too course, perhaps you could average the data, try using the ‘smooth’ node, it will clean up your signal and perhaps give you a more meaningful plot/view.
I would also reduce the Y scale so that the points are not vertically spread out like they are.
Next you have the legend itself.
This looks like it is made up of a few parts as well.
You might think about compromising by combining your end result to make this a bit easier to make…
You could use the ‘table’ node, this can be very powerful and flexible and may be all you need once it is tweaked to your data view.
Or you could look at using the ‘template’ node and build your own table view.
Combine the graph with a table, and you should be on your way.