Hello, I know that “Waves Audio” plugins are not officially supported on Audacity, but I’ve seen a handful of cases where people got them to work. I’ve tried over and over to install the Waves Audio Sibilance plugin but haven’t had any luck. Just reaching out to see how many people have had success with this, and if so, what did you do. Thanks so much!
So, this “seems” to work for me.
When starting 3.2.4 Audacity after installing the 7-day Waves demo, I get the message, “Incompatible plugin(s) found: C:\Program Files\Vstplugins\WaveShell1-VST14.0_x64.dll”
However, 4 new entries appeared in my Effect menu: Wave > Sibilence Mono, Sibilence Stereo, Sibilence Live-Mon, and Sibilence Live-Stereo.
I tried the first one and it changed my “less” into “leth”. 
I did not try real-time effects.
I am running 64-bit Audacity. You can check which 32/64 version you are running by looking at About Audacity > Build Information > Build Type.