Please, let me close task with dependencies (maybe also with Subtasks or Action Items etc.) without having to open them (i.E. in Gantt view, not sure if there are other views that have the same problem). Now, nothing happens and only if I open the task by clicking on it, it let me close it.

At the very least, give me a message on why it doesn't close. When there is no message (and simply nothing happens), I don't know if there are dependencies that prevent me from closing it or if the site is just buggy / timed out or something.