I was just scratching my head wondering why darktable doesn’t have such an obvious(??) simple feature: copying parametric masks between modules. I get that I can reuse a parametric mask by rasterizing it, but that doesn’t let me fine-tune the rasterized version.
So, is that feature just not there because nobody really needs it? Or am I totally missing something here? Right now, copying masks to other modules is a huge pain, especially when they have multiple parameters set.
Source image:
Copying and pasting the masked (exposure) module:
The parameters are copied, not the mask.
Drawn masks applied to a module can be copied, too, but I’m not sure how there the dimensions are handled – probably if outside the image, they are dropped.
Parametric masks depend on the image content. The only way to get the same mask would be to copy it to a duplicate of the original image.
@kofa is correct in that a duplicate of a module with a mask also duplicates the mask settings.
You could try creating a mask, then creating a preset and see if applying the preset also applied the mask settings.
Yes, that works, too, I have such presets (e.g. to apply local contrast in highlights to bring out cloud details, or to restrict contrast equalizer to the midtones).
I think the question was: how to copy paremectric masks between different modules within the same image?
Precisely 
If you do something drastic changes in the preceding module/modules then the mask is using that input and won’t really reflect anything like what you pasted… At least I would think this could be the issue in many cases
A parameteric mask is applied on data processed in the specific module.
It doesn’t make a lot of sense of you mask for luminance/hue (or whatever) using the same parameters on completely different data.
Copying parameters of a parametric mask is a feature I’d also like to have. Of course the resulting mask might look different depending on where in the pipeline you paste it but might still be useful sometimes.
One specific case where I’d like to be able to do this: It happenend more than once that I startet masking in some module just to realise in the end that I’d actually prefer to use a different module instead for the same task (e.g. color balance instead of RGB primaries for some colour modification or the like) but would like to keep the mask parameters I just spent a few minutes on.
You can set the module to neutral settings (if possible; for example, colour balance rgb features a bit of built in gamut management that you cannot disable), and reuse the mask as a raster mask.
Others have explained why it is not possible to copy properties of a parametric mask, but at least now the raster mask can have refinements such as feathering applied. This certainly improves the capabilities of using the parametric selection of one module as a raster mask in another.
Sure, I actually did this once or twice in the past but IMO its a rather messy workaround that can be quite confusing. Usually I rather transfer the mask parameters manually in these cases.
This was just meant to give a real-life scenario where copying the parameters would be useful.
Copying the mask makes no sense, but copying the parameters can make perfect sense when dealing with photographs of the same thing.
To some extent, it can be done using presets. For instance…
One of my exposure-module presets is called gold ribbon. The purpose of it is to kill the over-bright reflection of this metalic-gold ribbon in the dark-blue stage back curtain.
Essentially, it is a parametric hue selection. It almost-always works for all the hundreds of pics I take at that venue. What I have to do is to check the mask, for every pic, to see what else it is affecting, and if necessary, just add a drawn-mask brush line to limit its effect.
It is perfectly portable to many images, but not to other modules except by the raster method.
thats the use case for creating a preset containing a parametric mask 
same module, same intention …
Yes, indeed. But it may easily turn into different module, same intention.
