@Shikii – currently all development on the Processing IDE is focused on Processing 4, which just released beta 1. You could open an issue there with a feature request.
However, unlike Visual Studio Code, I believe that Processing IDE does not have a “plugin” architecture that could support a Discord RPC / GamesSDK api. It doesn’t have plugins in that way, and internally it doesn’t generate events and allow plugins to hook into them. So I suspect that Visual Studio Code is the way to go.