For the 2021 version there are Silence features in the Audio Edit window, but for precise volume adjustments for parts of the waveform it is best to either export your track to a DAW program for further editing, or upgrade to the 2022 version.

In addition to Jim's suggestion about the drum stems, the 2022 version has a volume automation feature. So even if stems are not available for your particular RealDrum track, you can still make volume adjustments to its waveform in the Audio Edit window. The Volume Automation feature is shown at 51:18 of this video: https://youtu.be/BS0yuTwhcCc?t=3078


Best,
Chantelle