I would like to have a focus per DSP parameter. This focus could be available renoise.song().selected_parameter_index and should always be set to the latest clicked/changed dsp parameter.
This way I would be able to use my jog-wheel (or keybind) browsing thru parameters before changing them.
Here is a related suggestion on how to display this selection, but it should probably be designed much less obtrusive. Dsp Keyboard Navigation
+1 if you think this would be natural 
EDIT: I see that selected_parameter_index is already taken for the automation view, so maybe selected_parameter_focus or something then.