As instructed on the plugin settings page, you may replace the default caret-down with any other Dashicon. Just visit Mel Choyce's list of WordPress Dashicons on Github, copy the whole CSS including "content:", paste it as a "custom icon" and save. The selected icon will then be used for the menu toplevel item(s), both responsive and normal.
I have currently no plans to improve this process, which I believe is relatively straightforward, of course this appreciation may vary.