The Watch Expression input box is where you specify the watch expression you want to add to the Watches window.

The default expression is the word at the cursor in the current Edit window.

You can use the history list to reenter previously entered watch expressions.

When you type a valid expression and press Enter or click OK, the debugger adds the expression and its current value to the Watches window.

If the Watches window is the active window, you can press Ins to insert a new watch expression.