You can add any of the four Day One widgets on the Today View on iOS. Starting in iOS 14, users can add these to the home screen for additional customization. There are now different size options users can choose for Widgets.
The options are Daily Prompt, On This Day, Streak, and Today. See this guide from Apple on how to enable widgets in iOS 14: https://www.apple.com/ios/ios-14/features/
This widget will display the Daily Prompt each day. Tap this to open Day One and start an entry with the prompt at the top. Prompts already answered will have faded text.
On This Day
This widget shows entries from the current date in the past. Tap this to open directly the On This Day view in Day One.
This widget lets you keep track of entries created each day. Tap a date to start an entry.
This widget displays information from the new Today view in Day One including photos taken, location information, and calendar information.