Clicking on Markers in the menu bar opens the marker window:
In the upper part the markers of the data point closest to the mouse cursor is plotted.
In any plot via right mouse-click a marker can be fixed in the lower part of the window. For this right-click on the plot window and select "save marker under cursor"
Right-Clicking on the marker opens a menu where makers can be deleted, shown as point to line in the plot and saved to an Excel file. The name of the marker can be changed by double clicking on it.