This is a really interesting discussion. I’m a professional musician. If a work that I have to prepare isn’t already “in my fingers” then I have to make up a process for learning it. Difficulty/length/complexity vs time are my variables to work with. I don’t make lists. Instead, I mark my musical score extensively, bracketing what will need more attention. Then I structure my practice sessions around those zones. But, as a rule, I don’t “program” them in a rigid way. I do make use of journal in which I record what I worked on today. From that, my clarity about where to go next emerges. I suppose for me it’s about injecting just the right amount of structure while allowing the whole process to still be a creative act. Maybe something in that for you?
Reading through the comments, I wonder if you put unreasonable pressure on yourself about the pace of your acquisition of the material. If the pursuit is truly for enjoyment, then letting go of expectations about the outcome can paradoxically lead to better outcomes! But maybe I’m over-interpreting here.
For your hobby of music though, constantly pivoting between the technical and what goes on in the sound world can only help. Again, with music, patience and careful listening to yourself are key. I tell my students that the practice room is less like a gym and more like a laboratory. Bringing a spirit of experimentation and playfulness can help in ways that over-objectifying the material and over-structuring it cannot. And in the making of music, knowing and doing have to be unified; that's the nature of embodied cognition.