Lukas, i don't think there are any Debug options built into the new 3CXPhone as of yet however there is a log file you could look at here %userprofile%\AppData\Roaming\3CXPhone for Windows\Logs
Barge in is available in 3CX v12, you have to have the new 3CX Pro licenses and you have to grant your users rights through the new group rights.