I’m still new to Inkscape, and if you are, too, then you know that cropping is a pain. To crop a bitmap, I had to change it to a pattern, first. Then, the intersecting path technique would work, and that is making a shape over the “pattern” to start. The shape covers the area that I want to crop, and then, I select both the shape and the pattern by holding Shift and clicking each. That’s when the Path’s menu item, Intersection, will crop the shape out of the pattern, but I couldn’t trace the pattern yet because it had ceased to be a bitmap; and reverting it back to an object reverted it back to its original shape; so I had to export it as a PNG. Then, I deleted the pattern, imported the PNG, and traced away!
cropping a bitmap to trace in Inkscape