Thanks,
I mean not add variable to watch but once inspect it in window.
i don't know what you mean? Can you show a screenshot?
Do you mean this:
Settings->Debugger->GDB->Default->Evaluate expression under cursor?
Now you can hover over a variable with the mouse and codeblocks will try to show you a small window.
For better usability you can activate
Settings->Debugger->Common->Require control key to show the 'Evaluate expression' tooltips
So you hover over a variable and press the ctrl key codeblocks will evaluate the variable