Hello,
Based on operating system compute the ScreenPercentage = 100 / (OS DPI Scale). For instance my OS DPI scale is 150% in the Windows display settings, so it will do ScreenPercentage = 100 / 1.5 = 66.66. This is quivalent to UE4’s Editor Preferences → Performance → Disable DPI Based Editor Viewport Scaling
Note you can also override the editor viewport screen percentage project settings in the Editor Preferences → Performance → Viewport Resolution.