Options can only be modified on startup, which seems excessive given it's a visual mod... I want them less prevalent, not invisible. Thanks!

That’s how the engine works. Sprites are defined on startup so the game can process them into an atlas and not try to load them during gameplay. There’s no capability of changing it mid game.

So you can't alter their transparency dynamically? You don't have to edit them physically this way. It's surprising you could not alter that although it's probably a more involved process.

Utility sprites don’t allow transparency as part of their definition as they just use the Sprite definition which lacks it - https://lua-api.factorio.com/latest/types/Sprite.html . There’s no way to make them transparent except to make the png itself transparent.

Got it, thanks for the explanation.