My scale settings slider (at the video settings) stays the same for me if I switch between the input modes?
My screen res: 1920x1080 -> using Nvidia Dynamic Super resoution (DSR) to upscale to 3840x2160 via Geforce Experience.
But also tested without DSR in native 1920x1080.
Slider was set to 1 (default), 0.8 and 1.0645744800568 (values checked via inspection tool merTorchbug, inspecting via chat command
Code:
/tb Options_Video_CustomScaleSlider:GetValue()
while the video settings panel was shown
Switched to gamepad/keyboard mode via keybinding and manually via the settings menu.
So I'm not sure what exactly you mean/talk about if you say "scale" here or maybe any other adodn of yours forces the scale to change?
Did you try with all addons disabled?