This script will give all links on your wordpress website UTM codes. Almost definitely works on other sites, haven't tested it. The utm_id will give you the index that the link appears in a Nodelist of all <a> tags. Could be optimized to look for an href instead of <a> tags, but I made it quick and dirty for my own purposes.

GiveAllLinksUTMCodes.js

function makeAllLinksHaveUtmCodes() {
    
    let linksArray = Array.from(document.querySelectorAll("a")).filter(function(item){
		return item.href&&item.href.split("?").length==1&&!item.href.includes("wordpress"); //returns items that have an href, no query, and aren't WP links
	});
    
    console.log(linksArray);
    let pageTitle = document.title.split("-")[0].trim();

    let linkID = 0;
    
    linksArray.forEach(function(link){
        link.href = (link.href.split("?")[0]+`?utm_source=${pageTitle}&utm_medium=website&utm_id=${link.id || linkID}`).toLowerCase();
        linkID++
    });

    console.log(linksArray);
}

makeAllLinksHaveUtmCodes();