This is similar to what I do. I have 2 main lists I operate from. One is what absolutely HAS to be done on a specific day. And the other is just a running list of the things I want to get done, but necessarily don’t have a specific date to finish. I put most important at the top, and then as I finish up the “Have To” list, I work on the 2nd list. Because I have to coordinate so many different schedules, I use Google Calendars to keep up with everything. It is not only free, but I can also manage multiple calendars all in one “main” calendar. I can also add events and appointments to family calendars. I can also use Tasks and Reminders in the Calendar, and use the “All Day” appointment reminder to set specific starting and ending dates.
We’ve also done something similar to our homeschool lessons. I would set 180 lessons for each subject, whether on paper, or digital (we’ve done a mix of both over the years), then my youngest could work at their own pace. So they just moved from lesson to lesson, rather than date to date.