Creating subtasks is difficult because completed subtasks don’t seem to hide; or we need them visible.
You end up with a long list, where completed are toward the bottom (and partially hidden… ugh) and new unfinished subtasks on the top of the list. You also must sort the unfinished subtasks to the top of the list manually.
Then to create a new subtask you have to click on a task near the top of the list (or it will create a new subtask at the hidden bottom of the list), then scroll to the bottom of the list and hit the new substask button, then don’t scroll to the top of the list, start typing right away or it deletes your new subtask and you have to do it all again.
There must be use cases where people want that at the bottom. Whatever happens when you try to make a new subtask but don’t start typing right away and it vanishes makes is difficult and seems like the new subtask button should be at the top of the list or both.