You have to do it in 2 steps: first create the graph and then include the dataset to be plotted.
Still 2 steps, but you can use the worksheet -s and then worksheet -p commands. This selects the dataset to plot and then plots the current worksheet selection.
You also don't need to use win -r to rename. You can do that by using win -t plot origin graphT50;
You could define a macro, so that you would only need one command.