To add some informations:
In standard cbp files, there is an environment variable defined as:
<Variable name="WX_CFG" value="" />
When it is used in standard cbp files, as:
<Add directory="$(#wx33_64.lib)/gcc_dll$(WX_CFG)
there are no problems.
In my unified workspace/cbp files, I define a wxwidgets path as, in my case, C:\wxWidgets-3.3.1 as the base, and in a user-defined field, I have created a wx_cfg variable. If I set this variable with nothing (an empty field), the variable is eliminated after a click on the save button. It's why, as in standard cbp files, I tried to set an empty string by "". Apparently, this is the problem described by ollydbg when I use a variable as:
<Add directory="$(#WXWIDGETS)/lib/gcc_dll$(#WXWIDGETS.WX_CFG)