I totally understand, it needs to stay simple or else it will become enough like the DAW's that have such a steep learning curve that it becomes a major barrier for entry. It would lose something that makes it really special.
That being said, Beepbox does it pretty simply, it itself being an app that's intuitive and simple to use. Iirc, you simply hold the button that places a note and drag it to another note to bridge it.
**Edit, I actually just checked it out, you hold alt, then drag the note to bridge.