I recently noticed that there were any wiki page on this awesome layer made by dooglus on 0.62.00 release.
So far I decided to add some light on that Synfig feature and make you know about how wonderful things can be done with it.
Here is the result: wiki.synfig.org/wiki/Curve_Warp_Layer
I think that it is fantastic for tails and tentacles and also to achieve interesting shapes using gradients.
I hope you like it!