Is there a keyboard shortcut or menu option to edit a selected text box in Keynote? I can edit the contents of a text box by double-clicking it. Are there any key commands to do this?

Here's why - I have a text box A behind a shape B. I can select the text box easily using the objects list or  using tab to toggle from object B to A. But once I have the text box selected, how can I edit its contents?

UPDATE
Here's a gif to make my situation more clear. I have a text box beneath a rectangle. In the video I 1) click the rectangle, 2) click tab to select the text box, and 3) double click the text box to edit the contents (but this doesn't work). How do I edit the text box without bringing it in front of the rectangle?
If you open Keynote and click on the Help menu item there is a line that reads Keyboard Shortcuts. Click on this and the following panel will appear.



in this panel click on the link in the middle of the panel and get this new pane shown below.



Now if you click on Select Text you get the following selection of shortcuts.



Maybe the shortcuts you want are under something besides "Select Text" in which case you can try another selection.