Reply To: RE: Layers and send to back
The elements are added to the active layer. You have to select the active layer in the Layers sidebar clicking on it. All elements you will add to the diagram canvas will be added to the active layer. The layers are rendered as follows: the last layer in the list (in the Layers sidebar) is rendered first, the first layer is rendered last. If you want to move elements from a layer to another one, select them, right-click on one of select elements and choose Move To Layer / Target Layer.
Send to Back and Bring to Front work only within a layer and cannot move an element to another layer.