I have seen that inside ....\src\tools\test\macrosmanager there is a macrosmanager.cbp file. It can display variables in the C::B log window if you launch a build or full rebuild command. The display is a little bit heavy/confusing, but it exists!
Oh, yes, this is a command like project, I see there are a lot of command line statement when you "build"(actually you do no build the project, but just run the command) the project.
<Add before="echo Code::Blocks location: $(CODEBLOCKS)" />
<Add before="echo Code::Blocks APP_PATH: $(APP_PATH)" />
<Add before="echo Code::Blocks DATA_PATH: $(DATA_PATH)" />
<Add before="echo Code::Blocks PLUGINS: $(PLUGINS)" />
<Add before="echo Code::Blocks LANGUAGE: $(LANGUAGE)" />
<Add before="echo Code::Blocks ENCODING: $(ENCODING)" />
PS: in some of the clangd_client_wx*.cbp, the $(CODEBLOCKS) variable is still used.
Let me fix them, I can find them by search the $(CODEBLOCKS) in all the *.cbp files.