There are 2 repositories under midi-plugin topic.
MIDI Plugin made with JUCE for interacting with microtonal piano layouts
A multi-track & polyphonic arpeggiator plugin that takes both chords and arp patterns as live MIDI data
🎹 Simple MIDI note repeater plugin (VST3/CLAP).
Pitch sliding for MIDI plugins (LV2)
Various Cockos Reaper JS MIDI plugins (effects)
Filter Channel specific CC data using Logic Pro X Scripter plugin