I assume you are talking about Custom Code Workflow Actions. In that case: Yes, you can change the version. There is a little dropdown at the top of the code in which you can change between v3 and v8.
If you found this post helpful, consider helping others in the community to find answers faster by marking this as a solution. I'd really appreciate it.
That's odd. Maybe this is new and didn't roll out to all portals yet. @Jaycee_Lewis do you have some more insights on that. In my memory, the dropdown looked different in the past also.