Rough transitions between filters

I’m using Audacity 3.1.3 on Windows 11

I am trying to add a distortion effect to mimic a growl/scream in high vocal ranges with a vocal synthesizer. However, only certain parts of the track should have the effect. If I apply the effect to only one part of the track, the transition is very abrupt and awkward. Crossfading does not seem to be helping, probably because of the small size of the clips I wish to apply the filter to, or maybe because I’m just not doing it right.

This is my first time using Audacity so I’m not experienced with it.

I attached an image of the track and indicated the portions I want to add filters to with blue.
Screenshot (14).png

To achieve a smooth transition between those portions the crossfades would have to be about a second in duration.