Google Tasks

Google Tasks lets you create a to-do list within your desktop Gmail or the Google Tasks app. When you add a task, you can integrate it into your Gmail calendar, and add details or subtasks. With the updated Gmail design, Google Tasks is sleeker and easier to incorporate into your work routine.

How to use G Tasks: https://www.oberlo.com/blog/google-tasks

G Tasks Guide: https://zapier.com/apps/google-tasks/tutorials/google-tasks-guide

G Tasks Tips and Tricks: https://www.androidcentral.com/google-tasks-tips-tricks