On Hypernodes there are several editors available to make your changes to your files.
To configure your editor, you can either export the EDITOR variable in your environment, or change the .selected_editor file in your homedir (/data/web/)

Set your editor using environment variables:

Set your editor using the .selected_editor file to Vim:

Or use Nano instead:

Now after configuring the editor, crontabs will be edited using this editor. You can open files using the sensible-editor tool.
This selects your editor depending on the configured settings.