The new Release 20.03 is out! You can download binaries for Windows and many major Linux distros here .
<wxPanel wxs="wxsmith/wxsTreebookParentQP.wxs" src="wxwidgets/defitems/wxstreebook.cpp" hdr="wxwidgets/defitems/wxstreebook.cpp" name="wxsTreebookParentQP" language="CPP" />
It seems never existed?