Here are my sure-fire instructions, developed on my Studio 11.1.1 installation...
Read just the "bold text" for the short version (it is really simple)...
- Start a new project
Use "timeline" view
- Add some video to the timeline so you have something in the project
- Add some audio to the project
It can be WAV or MP3
It can be on either the "sound" or the "music" audio track
My audio files were all over a minute long
- Use the razor blade to cut the audio in half
- Edit the volume on the right-hand (second) half of the audio...
- Use the mouse on the audio track to drag the volume line up or down
That will introduce your first volume handle
It is already "broken" now
- Try to change the volume of your existing volume handle
The "first one" will not move, you will get a new handle at the new location
- Try to delete the volume handle by doing a right-click and "remove volume adjustment"
It will not delete
Observations...
- Once you cut the audio with the razor tool...
("Before" and "After" mean their position on the timeline...)
- Everything before the cut works great
You can make, change, and delete volume handles
- Everything after the cut fails
Basically you can create volume handles, but once created you cannot modify (move) them nor can you delete them
What I have not yet tested...
- I did not test using an AVI as an audio file
- I did not test using a WMA file (from music ripped to Windows Media Player) yet
- I did not test short audio clips (my audio clips were all well over a minute long)