Add a point at desired location and put that on layer which is set to hidden and depending on your SW version, you can set that layer to be excluded from printing.
One approach might be to add either sketch points or sketch lines to your sheet format and set them to a layer that you keep hidden. To use them, the layer would need to be temporarily set to visible. A note can then be dragged and snapped to your sketch entity. The hidden layer visibility would then need to be turned off again.
Your placed note would in no way be anchored to this location. You would need to apply the "Lock" anchor within the note property manager.