Duplicate fingering should replace existing entry
In other words, if I try to apply finger 2 to a note that is already marked as finger 1, the 1 should normally be deleted. A right-click or other option would be used to override this. However, we currently have the fingering palette overloaded with fingerings, string numbers, and other details. To distinguish a (normally incorrect) duplicate fingering, e.g. 1 and 2 on the same note, from a valid overloaded notation, e.g. 1 and m and string 2 on the same note, we must be able to classify the fingering palette entries into groups, e.g. fingers 1-2-3-4 should be a distinct group from string numbers 1-2-3-4-5-6, fingers p-i-m-a-c, etc. A given note should normally have at most one entry from each group. In cases where multiple values need to be specified, an exception mechanism should be present. However the interface should optimize for rapid entry of the normal case -- which is at most one digit from each fingering group.