Thanks! I will follow both of you’s advice and rediscover my current system. It might teach me something about it as well.
If I find the time and motivation I might do both and see how they compare. In any case I’ll have two structures I can compare. If they end up similar I know I’ve wasted time. 
Not concerned with breaking history as the boundaries are well defined. I know each place it exists, much thanks to the index!
(Yeah… Todo is such a catch-all phrase for stuff that exists on a spectrum, and I find it difficult to know where to put it. Must-do, should-do, could-do, might-do, will-do, won’t-do, takes-5-minutes, takes-a-week, takes-5-months-but-I-really-want-to-remember-it, context, relationship with projects, dependencies, …
Maybe you can invent a complementary system for tasks as well?)