I've come to the conclusion this isn't actually a problem. If you don't think of your to do list as a tool for organizing projects but merely of a list of thing

I've come to the conclusion this isn't actually a problem. If you don't think of your to do list as a tool for organizing projects but merely of a list of things you need to do, you don't actually need sub tasks. But you do, of course, need to block some time every now and then to take a bird's eye view of where your projects stand. This works for my, but YMMV of course.