how do you insert icalendar items into todoist?
unfortunately, that's not possible right now. Currently you can only export Todoist tasks to a calendar using the iCal feed.
Thank you for the suggestion, though, we appreciate it and will consider adding such feature in future development.
You're welcome to add a feature request to our Votebox:
What is an iCal feed?
the iCal feed allows you to synchronize your Todoist tasks with calendars that support this standard (incl. Google Calendar, Outlook etc.).
To use it, simply go to the Todoist Preferences (top-right corner) and in the "General" section at the bottom of the page you'll find the iCal feed URL, which you can use with your calendar.
Here's an example how you can sync Todoist with Google Calendar: