For exporting yes, I think we only can export to root, but I think that downloads works for importing, at least I think I remember David mentioned something like this.
But, it would be really nice if we could set some directory for importing and exporting on all platforms. In that case we could use third party cloud option, e.g. Google Drive and automatize sync between platforms, which would make exchanging save file between platforms and devices very easy.
And, in long run, it would make David's life easier, because we would easy setup cloud save file exchange by ourselves.
Hope David would consider adding option for custom directory on all platforms, I'm not sure if it is that hard, but it would solve problem for easy save file exchange.