Likewise, the same applies to my office work, although obviously I can't just slot tasks according to time taken alone - this is because some tasks are more urgent than others and have to be done right away regardless of how much or how little time they take up. Instead of using NotePad or similar software for temporary stuff, I like to use an online scratch pad no sign up required, which in addition to space for drafting sentences, it also offers a to-do list section. However, stuff there can't be saved, so if I close the window it goes away.
On a slightly different but related topic, I think the space for free time management software is fairly open. There's a ton of paid subscription type of things, but comparatively little that is free (except for the free tier/trial of a paid plan). If someone were to make an open source version that could be run on the user's main device, it would probably get quite a bit of usage.
Of course, with any type of sofware, once it has to be on multiple devices with syncing, you're getting away from freeware for the simple reason that someone has to pay for the overhead costs of storing that data online somewhere and syncing it. But on a single main device, there's no reason that there can't be open source (or at least free) time management software.
I do think that no-one can be productive literally all the time, or if they are, they are likely not happy. So it's OK to have evenings and weekends be more free-form, especially if everything else can be fitted into the week reasonably well. Inevitably there is always going to be some laundry spill-over that goes on into the weekend but that is do-able.