tasks can not be assigned to big rock anymore

Since shortly, a task can not be assigned to a big rock any more during creation. Now only roles can be selected. Now the only way to create subtasks to a big rock is via -> edit task -> checklist.

Very unconvenient and slow compared to before. Is it possible to bring the old feature back?

(During creation of a big rock, it is still possible, but this brings the newly created task as "subtask" AND as "big rock")