You can use the keyboard to move the cursor forward or backward one character or one word at a time. You can also delete the character or word to the right or the left of the cursor, and you can move the cursor to the beginning or end of a line. See the Motion submenu of the Edit menu for the keystrokes specific to your computer system.
Getting out of an expression
Move to the end of the next-higher subexpression by pressing the Control key and the Space bar at the same time.
Selecting the next placeholder
Select the next placeholder by pressing the Tab key.
Select the previous placeholder by pressing the Shift key and the Tab key at the same time.
Move back and forth between complementary positions by pressing the Control key and the 5 key (or the % key) at the same time.
First we alternate between a radicand and an index.
Next we alternate between a superscript and a subscript.
Finally, we alternate between an overscript and an underscript.