You are right, Hector :o
The option to hide/unhide the line is a hidden property which is not exposed in the Properties pane, but only available via the Extended Editor (an option of the plot menu that is disabled in the standard WEST license).
All I can suggest (I know it will not be exactly the same) is to set the LineWidth property from 2 to 0 - the line will be very thin, but will not disappear.
I can try and push this into the next release (Nov 2021)