How to change Decks on Stream Deck based on modifier keys held

You can use this as a start:

• Remove all application triggers that start decks on the Stream Deck that you want to control.
• This script is now in charge of showing decks on your first Stream Deck device.
• In the "Deck IDs" section you need to paste in Deck IDs for the decks that you want displayed
• Right now deck1 will be shown by default, and deck2 will be shown when the "ctrl" modifier is held.
• To get the Deck IDs, select the Deck in the editor page, choose Cmd+C, then in the script editor, choose Cmd+V.
• To stop the script (for example if you've changed something and want to run a new version) use the Ctrl+Shift+Esc to stop all running commands.

Once you've figured out that this script works well for you, you could add a Finder application trigger to it so that it will always be started when Finder is in focus (it will take care of itself to not be running more than one simultaneously).

/* CONFIG */

//Select the Stream Deck device you want to control
var device = sf.devices.streamDeck.firstDevice;

//Deck IDs
var deck1 = 'user:cjy7orsth0001km10gr3cte4g:cjy7osmp60002km10pca66ryj';
var deck2 = 'user:cjy7orsth0001km10gr3cte4g:cjy8fnbdz0000xx10r6fow63c';

/* SCRIPT */
var lastKeyboardState;

function main() {
    var keyboardState = event.keyboardState.asString;
    if (keyboardState !== lastKeyboardState) {
        lastKeyboardState = keyboardState;


        switch (keyboardState) {
            case 'ctrl':
                sf.decks.get(deck2).showOnStreamDeck({ device: device });
                break;

            case '':
            default:
                sf.decks.get(deck1).showOnStreamDeck({ device: device });

                break;
        }
    }
}

function runForever(name, action, interval, timeout) {
    var now = (new Date).valueOf();
    if (now - globalState[name] < timeout) throw 0; //Exit if we were invoked again inside the timeout

    globalState[name] = now;
    sf.engine.runInBackground(function () {
        try {
            while (true) {
                sf.engine.checkForCancellation();
                globalState[name] = (new Date).valueOf();

                action();

                sf.wait({ intervalMs: interval, executionMode: 'Background' });
            }
        } finally {
            globalState[name] = null;
        }
    });
}

runForever("streamDeckChanger", main, 200, 5000);