This just depends on the type of widget you are interacting with and the type of input it needs. Under "Selected Objects" you can only choose the Environment Overview because the other widgets do not have any way to select objects. Under Selected Metrics the Metric Picker widget will allow you to select the metrics you want to see in the chart. I was initially confused by the Environment Overview also being listed there, but I'm guessing it will provide the Badge metric for whichever badge it has selected (e.g. Health, Workload, Anomalies, etc.). The drop down boxes will only let you select a widget the provides the type of interaction needed (select an object or select a metric).
