I've seen a competitors version of these auto schedulers, and they use your analytics to determine when the best date and times are for posting content to your audience. That recommendation would automatically show on the calendar for ease of use. The icon could possibly be the icon of the platform the data recommends posting to. For instance, if my audience is more active on my instagram post at 8pm on Tuesdays, or it receives a higher engagement to impressions ratio, the calendar would post an instagram icon in the corner of that time and day.
We already have exactly this on our Paid accounts :-)
We call the feature "Best Time to Post" and it shows up as highlighted regions on your Weekly Calendar. Simply click on the Cog icon on the Calendar page on the Web, and you can turn it on