I just fiddled a bit and it appears it's now mostly impossible, but can sometimes be done.
So:
1. all submitted and unsubmitted applications appear at https://portal.vantageapp.io/applications
2. unsubmitted ones will have a 'complete' button.
3. submitted ones they've specifically disabled it on the server side, so the ID that you would need to view the application is not there in all cases
4. in the Stephenson Harwood 'thank you for submitting' email it would say "You can view your application by logging into your Vantage account and going to the My Applications page. VIEW MY APPLICATION "
5. however this link is just a redirect to https://portal.vantageapp.io/applications and you can't get in
6. if you sign up for a firm's page at Candid ATS/Vantage at least a week before the deadline but don't submit they will likely send a reminder email. this appears identical, but is not - it doesn't go to portal/applications, but instead directly to the link to your application.
7. this will be https://shlegal.app.candidats.io/profile/create/[GUID] for SH, and e.g., https://michelmores.app.candidats.io/profile/create/[GUID] for Michelmores
8. My SH app is still viewable, but ALL my others (whether active or PFOed) appare not to be.
9. In addition to the 'please complete your submission' email, you can also find the correct link in your browser history - just type in "app.candidats.io/profile/create", and you'll find all the (recent! within your browser history) links to view your applications, but most probably disabled!!!