When you add an effect that can accept midi input, it will also become available as a “VST effect alias”. Select it inside the plugin selection window in the instrument editor plugin tab. Now select the particular alias and enter notes inside the pattern editor to trigger.
" Plugin Effect Aliasing
Most plugin effect parameters can be controlled by Automation or through MIDI Mapping. One of the things that cannot be changed by these methods though, is the effect’s preset (or program). Nor will a plugin accept note data. By treating a plugin effect like a plugin instrument though, these things are possible, and this is done by creating an Effect Alias.
Just put the effect into the track you want to use it on, same as usual, then go to the Plugin tab and select it from the FX alias list.
Now you can use a MIDI controller or an *Instrument MIDI Control device to send MIDI data to the effect and change the preset as a song is playing. Very few plugin effects accept note data, but for those that do, you can now play and record notes to control how the sound is being processed. The most common example of this are vocoders, but it really just depends on the specific plugin and how it chooses to use incoming note data.
You may find it useful to watch a short video on the subject."