I can be pretty indecisive sometimes with my art - even when I've already completed the line art and I'm in the middle of colouring or shading ^^; I made this auto action to quickly create a semi-transparent layer and a new raster layer so I can easily sketch over the other layers. Maybe you can find it useful too!
Edit - reuploaded to fix an error.
How it works:
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I don't like how I drew the mouth in this sample piece...
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So I can use the auto action to quickly create two new layers - one semi-transparent white layer to act as our "tracing paper," and one raster layer I can use to sketch a new mouth. It's a bit quicker than making new layers manually and helps streamline editing finished lineart.
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Once I've got the mouth looking the way I want it to, I can delete the tracing paper layer and fill in the colouring on a new layer under the new lineart. From here, you can flatten or merge the image as you like!
A couple things to note:
You can change the tracing paper layer opacity with this bar here on your layers window.
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If you check the box circled in the image, you can give your tracing paper layer a different name once you run the auto action.
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Feel free to adjust as needed! I think this may be a very niche tool but I hope someone else can make use of it! ^^