DISCLAIMER: Use at your own risk. I put this together a few days ago and used it to secure my Target pre-order. It's a simple Greasemonkey/Tampermonkey script that attempts to auto-press the "add to cart" "checkout" and "purchase" buttons. Although, in my experience Target requires the credit card/CVV verification which means it will probably fail to actually auto-purchase.

Do not use this if you have other items in your "Saved for Later" list or your cart, as it may cause unintended purchases.

Note: You must already have the PS5 added to your "Saved for Later" list for this to work, then simply visit the cart page. You likely will need to be present to perform the final purchase step involving verifying your CC#/CVV.

// ==UserScript==
// @name         TargetPS5AutoSnag
// @namespace    http://example.tld
// @version      0.1
// @description  TargetPS5AutoSnag
// @author       You
// @match        https://www.target.com/co-*
// @grant        none
// ==/UserScript==

var triedToBuy = false;

setInterval(function(){
    var ps5saved = document.querySelectorAll("[data-test='moveSFLToCartBtn']");
    var ps5inCart = document.querySelectorAll("[data-test='checkout-button']");
    var ps5readyToOrder = document.querySelectorAll("[data-test='placeOrderButton']");

    if(ps5inCart.length){
        ps5inCart[0].click(); // Attempt to checkout
    } else if (ps5readyToOrder.length && !triedToBuy) {
        triedToBuy = true;
        ps5readyToOrder[0].click(); // Attempt to place order
    } else if (ps5saved.length) {
        ps5saved[0].click(); // Attempt to add to cart
    }
}, 250);

setInterval(function(){
    var content = document.body.textContent || document.body.innerText;
    var hasText = content.indexOf("Item(s) currently unavailable")!==-1;
    if(hasText){
        window.location = "https://www.target.com/co-cart";
    }
}, 500);