If you have applied the process to a Preview of the image, then all you need to do is adjust the sliders of that process and reapply. The effect is instantaneous. I don't see what the problem is 
It is not a problem but it's a different "issue".
The DSE script has one slider: Amount. It governs the effect of the script as a whole. as I mentioned before, I found that the script often makes the already-dark areas too dark. I wanted to have the same amount of "darkening" in the not-so-dark areas but less darkening in the already-dark areas. So I added a couple of slides to control that (they could do other things, but to me that was the main use). So when you say "adjust the sliders" I'd say "what sliders?" since they were never added to the official version. And since this is not about me whining about "buaaahh they didn't add my sliders" I'll leave it at that
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