Fusion 9 viewer has added a new tool

"Show Gain and Gamma controls" (bottom right of viewer) has been added and shows up only when a node such as Loader, Fast noise or Render3D is active in the viewer.

There are times you can’t view all the information on the screen. This is where the built in gain/gamma adjustment in the Viewer comes in handy. Whenever you need to check if the colours are correct in really dark or bright area, simply tweak the viewer gain and gamma slider.
Nuke has had this for a long time and now Fusion has it.

well,
i can enable the new "gain/gamma" sliders on the viewer with every tool in the viewer...

Gain & Gamma sliders are gone, when "Show Controls" button turned off, but underlay still visible. In my opinion Show Controls button shouldn't affect Gain/Gamma sliders at all.

I wondered why I couldn't see these sometimes, now I know. Nice pickup.