I think you might be referring to System Audio that is captured when recording Software Simulation. You can disable it by deselecting the checkbox for System Audio when you begin a new Software Simulation. To make this setting persistent for all future recordings, close any open projects in Captivate but keep Captivate running. Open the Preferences window and navigate to the Recording / Settings Category and deselect System Audio. Click OK. From this point forward, System Audio will be deselected for all future projects.

You will see two audio recordings in your timeline for existing projects you are editing. Delete the one for the captured system audio that you don’t need.

Here is my answer in video form as well: https://youtu.be/NbsWvplZtOY

I suppose you are pointing to Adobe Captivate? Can you please be more specific?  When you mention ‘system audio’ it could be that you talk about a software simulation or a Video Demo which are both captured. It is possible to indicate ‘not’ to capture system audio, which is even the default setting.

However if you are pointing to a normal cptx-project where you have inserted interactive objects like buttons (all types), Text Entry Boxes, it is possible to take out the Clicks using the Properties panel of the interactive object. By default it is turned on. See the included screenshot.

Let me know if this was not what you are looking for. Turning on ‘mute’ seems to be a bridge too far indeed if you have narration.