Hello MauryaIsha,

If I understand well your scenario, I suppose that you are using property MoreIndicatorText. For example:

ultraChart1.Legend.MoreIndicatorText = "More...";

If so, than you are not able to disable/enable  this item ("More"), because this is just a Text Primitive to indicate that there are more items which are not visible due ti limited space. We have not such functionality to click at that item ("More") and to see all other series from the legend.

Let me know if you have any further questions.

Regards