No, you can load an input plugin into the first slot of the master section. It allows for real-time monitoring of incoming audio from your audio inputs. When using it, you can monitor through plugins in the master section in real-time as well. It’s similar to the external gear plugin, but in this case it’s for when audio is coming in from a different source (from outside Wavelab).
I use it for integrating my mixing computer - it allows me to mix (in Cubase in the other computer) and master (in hardware and in Wavelab) simultanrously… I also like to use the same technique when doing mastering work for people… playing back from Cubase on the other machine at whatever sample rate, going through whatever analog gear I want, monitoring into Wavelab, and through whatever plugins in Wavelab I want - all in real-time. When I’m happy, I record the audio from Cubase and my analog chain as a clip into Wavelab’s audio montage, and then drag the effects i was using in Wavelab’s master section into the “clip fx” for that clip… then repeat the process for the next song. The entire montage is assembled this way, and all additional mastering work is completed in Wavelab.