variable (“parametric”) urls

Creating such an URL doesn’t mean WP knows how to handle such a request. It would need a related rewrite rule that tells it how to use the elements of the URL. WP doesn’t really need to know the current user by URL parameter. WP knows the current user by their auth cookie. A page’s template could be coded to only display the current user’s personal content even though every user uses the exact same URL.

For example, this is how cart links work on e-commerce sites. Everyone views their cart at example.com/cart/, but each user will only see their own cart items.

There’s no specific cart example in my earlier post. If you need a specific example, go to Amazon, log in, and add an item to your cart. Go to the cart page to see the item. Notice the cart URL is /cart/view.html?ref_=nav_cart. All users get the same URL. What the page shows is unique to each user because we all have different login cookies.

Amazon is not a WP site, but the principle is the same. As long as the user is logged in, the same page URL can display unique content for that specific user. This is done by qualifying the query for content with user ID. A cart query would be for all cart items added by the current user. The query’s coding ensure’s no one could see (except admins) any other user’s cart items.

The “Press HERE” link you’re imagining can go to the exact same page for everyone, yet each person would only see their unique content because the related query would be qualified with the current user’s ID. Having a unique URL for every user like you imagine could actually introduce a privacy leak if a third party were able to correctly guess another user’s URL. Of course code could be added to prevent this. The point being that while a unique URL is possible, it’s not optimal since the needed user information is already in their auth cookie anyway. Site cookies are sent with every HTML request, so if they’re logged in, we always know who made the request, regardless of the URL requested. We can then tailor content accordingly.

OK, you can do that if you want. It ignores the advantages of a CMS system for a more stilted, rigid approach, but it’s possible. If a user name is included in a page’s slug and there is such a page for every user, simply include the username in the slug when creating the page. It’s important the remaining, common part (“mydomain-privatepage-“) of the slug always be correct. Make the user the author of the page and publish the page as private to keep other users from accessing the page.

If you want to give the current user a link to their particular private page, you need to first get their user object, then their username from that. Then concatenate it to the rest of the URL, like so:

<?php
$user = wp_get_current_user();
if ( 0 != $user->ID ) {
  $url = site_url("/mydomain-privatepage-{$user->user_login}/");
  echo "<a href=\"$url\">View your user page</a>";
} else {
  echo 'Log in to see a link to your user page';
}
?>

I’m not sure why you’d want “mydomain” in the page slug since it’s in the URL anyway. It’s more to get wrong when creating the page. IMO you should keep it simple, a slug more like “user-bcworkz”. Then a complete URL would be more like https://mydomain.com/user-bcworkz/

You know, WP already has a built-in variation of this: https://mydomain.com/author/bcworkz/
It leads to a page showing the user’s bio and all posts they’ve authored. It only works for users who have published a post, but admins can publish one for them in place of making a dedicated page like you intend. The main difference is this page is public. But you could alter author.php template code to only show content if the page is for the current user.