Share to dos with people

Hello,
I am now looking for longer time to find out how to share tasks with others. Fortunately I can share a created list with others but it won‘t solve my problem. In to do there were alresdy are lists where I can see my tasks from outlook and planner. Now I want to share those taks with others but I can‘t share these by to dos given lists. So I think I need to synchronize the given lists with my own list to share the task with others. The only way I found is probably with power automate. But maybe there is a easier way?

Short description of what I am looking for based on a practical example: The assistant should see all tasks of the general manager which are created by the gm in outlook, planner or simlar.

Thank you very much.