Thank you very much SirIn Data Display, you can use "File > Manage Dataset Aliases" to create an alias name for your simulation datasets. Then you can use that alias name in the plot instead of the original datset, and the legend will show the alias name.
Another possibility is to use equations. From the menu: Insert > Equations.
e.g. Circuit_Parallel = Parallel__20_Sweep_Cf..Rendement
and then use Cicuit_Parallel as the plotted data