Note: In the latest release of octane render, you can no longer stop your render part way through and still have the PSD file save. This means you must set a set amount of samples for your scene to render, and then have that amount of samples rendred.

If you would still like the flexibility of rendering as long as you want and then just stopping when it looks good. Like I'm used to doing, check out this video here.
https://store.epicjcreations.com/courses/octane-master-course/40513-octane-v4-0-updates/245770-03_a-different-way-to-save-still-renders