Olympus Highlight & Shadow Control affects the JPEG rendering, not the underlying RAW capture. That means it does not change the sensor’s recorded data, alter sensor gain, or compress the RAW file’s dynamic range at the time of capture.

On newer Olympus bodies, the setting can also be applied later when doing in-camera RAW processing, which reinforces that it’s a rendering adjustment rather than a change to the original RAW data.

So if you shoot RAW, you can generally make equivalent highlight/shadow tonal adjustments in post-processing. If you shoot JPEG, the camera applies the effect to the final image.