I was thinking about something like this but for fall velocities, you would have dropv value displayed onscreen and you could change it then make enemy fall with changed values, then you could take a looks at the value if its what you want and copy that to your dropv in text file.
I wish there was something like this for fglayer, where you could manipulate all values of flayer displayed as text onscreen and could easily create parallax effects that you want because changing them one by one and restarting levels to see it is time consuming.