Right now, when you schedule a task from one of your lists for a date, the task gets moved to that date, and it disappears from the list it used to be in.
That sometimes causes issues for me for several reasons: sometimes I don’t keep track of my daily scheduled tasks, and then one of the tasks I had to do slips through the cracks, because I don’t see it in its list anymore. And some of the tasks I have in my lists are things like hobbies that I repeatedly do, so it doesn’t make sense for them to disappear from their list just because I have scheduled them once.
I suggest having a toggle option somewhere, that allows users to activate “copying a task from a list onto your schedule” instead of “moving a task from a list onto your schedule”.
That way, tasks can remain on their list, even after scheduling them, if we want them to.