When pressing Tab You can set the Tab key to do one of two things: Indent the currently selected item in the outline, thus making it a child of the item above it; pressing Shift-Tab outdents the selected item.
Move to the next cell in the outline; pressing Shift-Tab moves to the previous cell.
Either way, the Indent and Outdent commands in the Structure menu (and their keyboard shortcuts, Command-[ or Command-] by default) will always work.
You can always press Option-Tab to type a tab character at the insertion point.
When pressing Return in a cell, create a new row When you are done editing the contents of a cell in the outline, you might press Return to finish editing. If this preference is turned on, a new item is then created. Otherwise, the editing just ends and the current item becomes selected.
Whether this setting is on or off, pressing Return while not editing a cell always creates a new item.
You can hold Command while pressing Return to temporarily change the setting; for example you could press Command-Return to finish editing and create a new item, even if the setting was turned off.