It's happened. Margie's assistant, Bernadette, has become so adept at running the business that she's now a partner. She needs to sit at the same level as Margie. Currently, there isn't an option to add her as a Coworker at the top level.
Turn off AutoLayout
To be able to move shapes around freely, you must turn off the chart's automated layout default—set by the AutoLayout command on the Org Chart toolbar (see the picture on the left). When you toggle AutoLayout off, the shapes in the chart become subject to AutoShape rules rather than org chart rules.
But words of advice first...
When you turn off AutoLayout, you lose some of the automation you may want as you build your chart. For example, automatic branching ("left hanging," "right hanging," and so on) isn't available without AutoLayout; so get your initial layout in place before you turn it off. Also, when you insert shapes, they don't automatically go into position.
Another consideration is how you style the chart. The best advice is that if you know you'll turn off AutoLayout to do some chart editing or restructuring, style the chart by hand. Style Gallery styles will persist in a shape even when you move it to another position.
Finally, once AutoLayout is off, leave it off. If you turn it off and restructure by hand and then turn it back on, you'll lose the restructuring. So only turn it off when you're ready to leave it off.