The default key to open the gui is "C", but it can be changed in the keybind settings.
This mod offers the ability to keep track of to-do lists in-game, using priorities and the ability to cross-off items and complete lists.
It also has a nice statistics screen to show your total quests(to-do list items) and how many of each priority you currently have.
Furthermore, there is a screen to add notes, to keep track of important coordinates or other important information.
Please make sure to turn off menu blur in the accesibility settings.
All the stored notes/quests will stay when you exit and restart the minecraft isntance.