Can't wrap my head around GROUP BY - dataview

I don’t know if I follow you…

  1. In your query the first issue is: you need to apply rows to file.tasks.completed, i.e., rows.file.tasks.completed.
  2. Why you want to join? I think you can’t get what you want, because it always shows a “,” between your bullets (because multiple tasks in each file and other strange behaviors that I don’t understand), etc. Besides that, a mix of “●” and “○” gives you any ideia without relation to the specific note?
  3. Why you don’t use a kind o progress bar like this (per file): Progress bar for incomplete/total tasks?
    (gives you a progress bar similar to this html that you can put directly in one note to test:
<progress value='75' max='100'></progress>