Steps to reproduce:

1. Create a Graph widget and add hosts to the data set
2. Change the host's name or visible name

Result:

The change does not reflect in the graph data sets and has to be edited manually each time

Expected:

Data sets should work with the host name instead of the visible name. This allows the visible name to be changed for usability purposes such as sorting hosts in groups in a certain way or using specific naming schemes. I am unaware of other cases where the visible name is used in such a way, but I think it would be best is the visible name was not tied to any functionality that is not dynamically updated.