Context / Shell menu integration
This could probably be done manually with a registry edit, but it would be nice if there were an option in settings to integrate this into the context menu so files can be sent to it directly from a file manager.
I agree.
Best you can do now is go to:
C:\Users\YourUsername\AppData\Roaming\Microsoft\Windows\SendTo
and drop the program's shortcut in there. It will appear in the Send To context menu when right clicking a file but unfortunately it doesn't load the file in.
As I said, you could make a registry entry to add it directly to the context menu if you don't want it in the SendTo submenu, but since the program doesn't accept arguments (e.g. file names), it will just load empty as you mentioned, and not with the file that was right-clicked, making these extra steps a waste of time. It would be faster to just run Hashing and then drag the files into it. But, of course, it would be ideal if it were made to work with right-clicking the files and sending them to it.