Thanks,
I missed the project wizard's checkboxes :oops:
http://wiki.codeblocks.org/index.php?title=Creating_a_Plug-in_which_modifies_CB%27s_Menus#Adjusting_the_.22Edit.22_menu
States
int pos = menuBar->FindItem(_("Edit"));
but I had to use
int pos = menuBar->FindMenu(_("Edit"));
I guess this is a misstake in the wiki. I did not change the wiki because I am a c::b greenhorn and not 100% sure about that ;-)