@tony.topazlabs It appears 3.3.9 still has this problem, as noted by a message from another user “pinkdong”:
“…I did run into a little inconvenience: I want to create a preset for upscaling to 4k at a fixed 8k bit rate so I select the built-in “Upscale to 4K” then I changed the encoder bit rate from “Auto” to “8k”. Now to create a custom preset, I have to change the preset to “None” first before I can create a new one. I wish that create function (+ icon) is added to all the built-in presets in the future.”