Like @kevin1, at this stage I would put Merging in the Too Lazy bin … i.e. let Sense do it when it gets around to it. Meantime, as other have pointed out you may actually want to account (and set Notifications) for the individual components of Devices. e.g. Fridge light on = Fridge door open = Racoon alert!
Consider: When Sense eventually does auto-merging, what it’s doing is re-aggregating electrical signatures (“devices”, small-d) while potentially keeping track of the sub-signatures of a particular “Device” (capital-D). This could retain the ability to trigger device-based (small-d) notifications or even display a Device (capital-D) waveform with all its sub-component device (small-d) waveforms stacked. Wouldn’t that be nice!