macOS Layout guides missing inside NSBox

[Qaanol]

I have a bunch of labels and text boxes (and checkboxes and popups) that I placed in Interface Builder. When I arranged them, I used the little blue helper lines that make it easy to align or center objects. Then I wrapped them all in a box.

Now I’ve decided to rearrange some things in the box. However, it seems that the blue guide lines simply do not appear when I am moving items around inside an NSBox. So I have no easy way to align the views.

I hope I’m missing something. When I drag everything out of the NSBox, then the guide lines work again. So I don’t understand why there are no such helper lines when I drag things around inside the box.

Any ideas?