When you use the GMail and the Chrome Extension to create a "New Task" from an email, it creates a new task and copies the email to the task. It also puts a link in the heading of the email to the newly created task. This means that if you view this email in the future, you can see that it already has a task associated with it and can click on the link in the header to go straight to the ClickUp task. It also appears that subsequent emails that are part of this thread also have this link visible (even if the contents of those emails doesn't actually end up being documented within the task, but that's another issue! More about that below).

If you create a new email from within ClickUp using the GMail integration, the email is visible in the GMail Sent items. It doesn't have a link in the header as in the example above. Although you can see it was created within ClickUp, because of the footer that is added, there isn't a way to jump from GMail back to the associated task and any subsequent emails don't get this link either (although the responses, do end up being part of the ClickUp task (which is referenced above as a limitation of the subsequent thread being sent to ClickUp).