I would like for Krita to have a tool where you can apply rectangle/square into the canvas, and you are able to export only areas where the applied rectangle/square are used. Overlapping areas is a bonus though not needed. Right now, there is no easy way to export sections of images that isn't of uniform size. The reason this would be useful is that there exists artists who work on multiple views of different concepts, and there are some people who would like a quicker way to extract section of images out of the canvas. This is especially useful for artists who works on several concepts, and also aids in portfolio or other purposes. While, there is image split tool, it isn't useful when 2 or more concepts are not aligned right. That's the problem right now.
Related to bug 397172. It could be implemented easily in the less convenient for the user way by just writing down both the size and the origin point just like the Image -> Resize Canvas do. In such case it would be best to implement both this and bug 397172 at the same time and in the same dialog. This wish can be however also considered as a request for more interactive tool like Crop Tool, but just for temporary marking the area for export.