@liuliuforphIn the latest nightly builds the watches window has been redesigned and works differently that the one in 10.05.
Currently there are two ways of adding watches in it:
Click in the empty last row in the watches window, type the name of the variable (or full expression) and hit enter.
While the debugger has stopped on a breakpoint select a variable name or full expression, right click to open the context menu and then select "Add watch 'expression'".
The automatic inclusion of local variables and function arguments have not being reimplemented. Sorry about the inconvenience.