While selecting a shape, use the shortcut keys:
- [ to send backward
- ] to bring forward
This will position the shape behind or on top of another shape in the diagram.
If there are multiple elements, you can click [ or ] multiple times, or use Alt + [ or ] (Win) or Option key ⌥ + [ or ] (Mac) to move behind or in front of all of them.
For the non-shortcut method, select the element, then choose from the Stack order options in the floating editor:
In the in-app diagram editor, you can find the Shortcuts guide on the bottom right:
Clicking on it will bring up a popup guide on various shortcut keys in Cacoo.