It's possible, but only if you use track automation. It's disabled if you try to use clip animation, and if you try to use normal keyframes in the inspector, there aren't any.
If you're only used to keyframing in the edit page, track automation is slightly different. It's meant to let audio engineers record the movements of physical controls, like faders, in realtime. You can get away with a mouse and keyboard if that's all you have, but it's a little cumbersome.
Make sure all of the automation buttons are lit (there are three; one next to the transport controls, one next to the track header, and one at the top-right of the noise reduction plugin). Make sure "plugins" is lit in the "enables" list, and select the parameter you want to automate from the dropdown in the track header (if you don't see it, make sure your track height is high enough.)

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