In Tracks view; they exist under the waveform or MIDI data.
You may need to pull the track down to expand it or hit the little arrow on the far left of a given track.
The horizontal line is the volume, you can move it up/down at a given point in time as desired.

They can also be accessed in the Piano Roll view.


Make your sound your own!
.. I do not work here, but the benefits are still awesome