today it looks like I can only have a canvas at the level of a product. But we are currently using the canvas to make sure a new Idea (that can be a new capability in an existing product) has sufficient business data available to judge the value of it. As far as I can see now I cannot create a Canvas for an idea. This reduces enormously the way we treat the idea funnel as input stream for our product innovation
It's possible to create an Idea portal which covers multiple products. This can be a way to add ideas which may relate across multiple products or product lines.
You can set this up through Settings -> Account -> Configure idea portals.