I suppose this may be possible to do but the Story Level Marker object would have to be modified and editable hotspots would have to be added to its script. Then it might working (but I have not tried to tell the truth).
As far as I know this isn't possible as the Story Level Marker is not a "selectable" element so there is no way of actually editing the hotspots.
Because you can't select the marker the hotspots never appear and hence can't be edited.
I had to resort to the settings dialog for our custom marker
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