The Bear Callouts webpage doesn’t provide any information for using Callouts in Apple Shortcuts. Specifically, how to make text, bullets, and todos show up under the Callout title but within the Callout box. This is as far as I get:
Here’s a link to my daily shortcut. But it’s set up to work with Apple Calendar and Apple Reminders. So, you’d have to connect your calendars and reminders and create dummy events, appointments, and reminders due today. Otherwise, you won’t be able to test it. But, here it is anyway.