When you select a tool and open the Tool Options bin below the image window, companion tools are displayed in the bin. Selecting a tool in the Tools panel opens the Tool Options, where you can select additional tools if you're using keyboard shortcut keys.
To cycle through tools that share a keyboard shortcut, simply press the key that corresponds to your desired tool until that tool is selected. For example, if the Elliptical Marquee was the last tool used, press M to return to the Marquee tool. Check out the keyboard shortcut for each tool in the Tools panel, as well as which tools share a keyboard shortcut.
Note: New in Elements 2019 is the Smart Selection tool.
