TL;DR: you can manipulate the Web Form Session 😉
Long answer:
Hi, every time time you start a session, there is a special record created in your Dataverse for a table called Web Form Session.
This record is related to your Web Form, and also contains a reference to the table/id of your main record (as string and not lookup).
This also contains the current step and all transition the user went through (step history). You can manipulate the Current Step / Current Step Index via Plugin/Workflow to set your record to be in a specific step.
Below snapshot is very old but can give you an idea:

ATTENTION
something very important here, if your Web Form contains conditions/branches, this can make your web form all confused, this is because the transition path has been disrupted, so if the user is trying to go back/forth they might have issues. In simple words, if you have conditional branches, please avoid this technique, or maybe you will need to read all the step history to understand where the user is coming from and setting a new history manually (that would be probably very complicated).
Finally, not sure how you are planning to manipulate this, but don't use the Portals Web API to manipulate Portal tables, this is not supported and if you get it working, it might stop working in the future. Look for server-side coding/workflow here (sync/real-time as you want to refresh the cache instantly).
Sorry about the long answer.