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We dropped out WebGL export from Boxshot in favor of Koru. All the cool WebGL features are there, please consider using it instead.
You can drag objects around the scene tree, dropping them one onto another to make hierarchies. Does it help or you need a more specific grouping feature?
There are almost 250 materials in version 4.13 and some new images, too :) http://boxshot.com/2017/06/05/boxshot-4-13.html
We have dropped out WebGL export from Boxshot in favor of Koru which is now free even for non-commercial usage. There's no reasons for us to keep two similar functionalities in two different applications. Consider switching to Koru for your WebGL export.
Boxshot doesn't have paths, so we can't make it for any path, but have a look at the new "Extrude" shape, hope it helps: http://boxshot.com/2017/06/05/boxshot-4-13.html
We'll add another template with the next update, showing exactly the customization of the built-in buttons.