Free Video Editor is said to be a lossless simple editor.
https://www.dvdvideosoft.com/free-video-editor.htm
VidCutter x64 is another. Not sure where you can find it.
I don't know if you can alter volume with them.
BSFAG supposedly can adjust volumes, but I think it involves a re-encode.
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It requires mp3gain and FFMPEG.
I've never used any of the above.
You can open a lot of video files in Audacity and then adjust the volume of the audio track. Not sure if that meets your requirements.