Integrate ToDo/Planner with OneNote
If you look for example at Dropbox Paper, they did something great...You have the ingredients but they are not yet well interconnected. The idea is that you can define tasks (with checkboxes) in many different notebooks and pages, but they will be automatically scanned and referred in your ToDo list at a global level.
The big problem with groups, channels and notebooks, is that, after a while, you won't find back important things to remember. With the cross-discovery of tasks/checkboxes in your notebooks and centralization of the global list, you will never forget something, even if it is hidden deep somewhere.