On the Visualize tab, you can just drag the .hlt file onto the page to see it. There was a local visualizer, but we scrapped it to focus on a single implementation.

The devs are actively monitoring the site's forums and you might want to take this there.

It would be nice to have a submit file button in addition to drag-and-drop. Not everyone is using graphical file managers with this interface feature.

This also makes it difficult to automate. Similarly, maybe I would like to automatically submit my new bot when I do a commit or a push, but the Submit button uses Javascript which makes this unnecessarily difficult. (At least for me.)