Hi I also needed to export a dictionary, but what I did was export the array like you did, and then increased the size in the editor, and scrolled to the bottom of the list to find Array, RawArray, IntArray, StringArray Vector2Array, Vector3Array and ColorArray. So essentially it becomes arrays inside an array, which is more or less a dictionary. Did the job for me .. !!! Hope it helps you too !!!
But yeah a dictionary would be much better. I hope and I think they have planned for the future, maybe it will be there in v3.0