Hi folks,
to have my tasklists clean I really miss my checkbox lists. Moving one item to the todo-list would automatically get a checkbox. Unfortunately this does not work any more. My lists getting messed up since this change. 
So my suggestion is, to bring the checkbox list back while keeping the individual checkboxes.
Why not introduce a checkbox list option comparable to the “number children”. You could replace the “Add checkbox to children” for that. Then the “Add checkbox” can extended to a kind of Tristate-Option:
-1 no checkbox eveb when parent is checkbox list
0 Take checkbox option from parent
+1 force checkbox independent if parent is checkbox list.
You could mark the three states by different symbols, that changes depeding of the item checkbox state.
Here is a mockup to illustrate the idea:
What do you think?