In the designer, a container can only be moved by using either the arrow keys or holding ALT and dragging with the mouse.
However, ALT is the windowmanager’s key. ALT-dragging is for moving or resizing windows. Windows might not have this vital function, but most windowmanagers in Linux do.
Moving with the arrow keys is deliberately slow to allow for precise positioning so that is not a usable alternative.
Please can this be changed or expanded so that CTRL can be used instead.