I've been busting my head around trying to make solid-looking trails and found that this guy had already figured out how to make it using WebGL.
He's posted all the source code to github.com/pyalot/webgl-trails
I am a mere mortal and understand little of such things.
Is there anybody who can make this work with Construct? I think it will be a great feature, as right now there is no way to make smooth continuous trails.