Thanks for clarifying—my mistake if I misunderstood, but I actually tested it on my setup and found I could drag and drop items directly from a folder in the Dock. Apologies if I misinterpreted the limitation!
We've released a new version(v0.1.0). You can now preview image files, text files, audio files, and more. Multiple selections and drag-and-drop are also supported. Please download and try it out if you'd like.