For some specific project, Highlight col(C)[1:13] and plot a line graph

Highlight col(C)[17:29] , then switch to graph to select Insert: Plot to Layer: Line
==> Plot is not inserted.

Highlight col(C)[17:29] and plot a line graph

Highlight col(C)[1:13] , then switch to graph to select Insert: Plot to Layer: Line
-->Plot is inserted. If you insert the second data as a different type of plot, eg. scatter or line+symbol, it adds the plot correctly regardless of order.