I am much obliged for your prompt replies - thank you. I think I may have solved the problem and if so please accept my apologies if I burdened you with any unnecessary work.
By experiment I discovered that if one has the title of a security visible on a chart (the gold letters on the black background border at the top of the chart*) then hovering the xhair fist over a candlestick signal marker will produce a label with a description of the signal.
However, if one scrolls the chart up so that the title bar* is not visible, then hovering over a candle signal marker wil not display a description label.
Again, please accept my thanks and my apologies.