isolines legend range vs. other components
Isolines legend is always created as a set of small lines representing created isoline values and colored with the same component. However, when color mapping is changed to another component the legend becomes obsolete - the range and lines are kept to represent the created isolines while legend title and color change to the colormapped component ignoring the coloring range. It seems that the proper solution is that the legend should be drawn as lines only when the same component is used for isolines extraction and clormapping. Otherwise a default legend bar should appear in the full range of a colormapped component.
To recreate use test field -> connect to isolines -> select both components to be interpolated to isolines -> switch on legend -> change colormapped component to Gaussian swirls.