Hey there community! I'm a PO also configuring JIRA. I am constantly trying to gather feedback on the JIRA usage from my engineers to make their lives easier. One thing I though about in the past is automating transitions using workflow triggers.
However, it did not went well because I and also the engineers are encouraging small batch sizes. So you have rather three small PRs, building your story up incrementally than one big PR. That said, you will run in situations where you will have multiple PRs for one story. So a workflow trigger would move the story back and forth between 'In Progress' and 'In Review' until the final PR is merged.
Small PRs are great, easy to review, easy to understand. However, not so great for workflow automation. Does anyone here has experience solving that problem?