I was able to export Metafields, but I couldn't get them to import which is why I installed the app in the first place. Exports are extremely slow, the progress bar has said it is 100% for at least half an hour for the export I just ran for just one order.
I loved this app, it was completely perfect for what I was doing, then they removed the ability to add urls without upgrading to the pro version, so unfortunately I'll be deleting it, as it no longer is useful to me
We bring forth to you so many new features which you could take advantage of along with adding and deleting metafields globally, we insist you to give it a try at least. We have so much to offer for free compared to most of the apps in the Marketplace. You can check for yourself.