A simple exposure control right in the viewport frame buffer.

Based on:
https://forum.corona-renderer.com/index.php?topic=44037.0

Either via the edit tone mapping button or the camera, changing exposure is too cumbersome for quick changes.

Most of the times you have another object selected rather than the camera. You need to select the camera first, change the exposure, and continue working with the object you were working initially.

With the edit tone mapping button it's two dialog boxes/windows just to change the exposure.

I think it would be much more artist friendly to have a simple box with the exposure right in the viewport frame buffer.