When you enter a variable/expression in the quickwatch window's expression text box, while debugging and press period, the intellisense lists out the members of that object.
The problem -
You can not select a member using the arrow key.
Instead, if you press up and down arrow, the the value in the expression changes to the previous / next expression or blank, if no prev-next expressions are available.
This is very annoying since you could select item from the intellisense list for years and people are used to it.