Kdenlive is a powerful video editor that I find hard to discover features in.
I’ve settled into a workflow where I record everything but the game play, then record the game play demo, then record a voiceover.
Usually it just gets the sound levels right, but sometimes they’re out of balance.
To change them, right-click on an audio track, choose “Insert an effect” then choose “Volume”
This adds a gain control to the effects panel at the top.
I’m trying on Kev Quirk’s “100 Days To Offload” idea. You can see details and join yourself by visiting 100daystooffload.com.