Just wanted to throw out there, when iPadOS is released and support directly from attached hard drives Is supported it would be great to be able to import.
Just a thought.
Steve
Thanks for the suggestion @Phoenixfire1965
We want to give as much support as possible to IPadOS, including external drive support.
Just an FYI here, I was using Panels on my iPad that was running iPadOS 13 and this worked just fine. In the import menu simply tap iCloud Drive and it will show the Files interface that allows you to import. That being said using this through Panels didn’t work with importing, I would need to launch the Files app by itself, then copy comics from my SMB file share into the Panels App folder on the iPad. When I next opened Panels, the app would see that I had added comics (like if you added via iTunes) and offer to add them to the library.
Great workaround 
We are also testing iPadOS 13 making sure everything works for the oficial release.
As you mentioned, we still do not support direct import from external drive, but we will try to support it from day 1.
When the official release date gets closer we will send some betas supporting iOS13 and we will be glad if you guys can help us testing them.