Entering newlines in content selector expression text area

While creating or editing a content selector, you cannot enter newline characters by normal means into the search expression text area. This is very annoying as longer and more complex queries can be written much more readable and maintainable if you can split them over multiple lines with indentation. But I was not able to insert a newline be pressing the return key alone or in combination with any modifier or modifiers combination. The only way I found was to copy&paste a newline character, but this is pretty cumbersome.