godotshaders.com is an awesome resource for sure! Glad I could help you with my list! And yes, it was way simpler to modify the shader parameters on the fly rather than to code an actual oscilloscope with godot nodes and scripts!
[SPOILER]
For the “all in rebellion” you need to befriend Bernard like you did, and also come back to previous islands (for instance going to the first islet in mission 2)! Glad you enjoyed the game so much that you wanted to play another run!
[/SPOILER]