Widget Settings
The settings are found in the Class Defaults of the BP_LowHealthScreenEffect blueprint.

Min Strength / Max Strength – controls the intensity of the effect based on the player’s health. When activated, the effect starts at Min Strength and increases towards Max Strength as the player’s health gets lower.
MinBeatsPerMinute / MaxBeatsPerMinute – controls how fast the heartbeat effect is based on the player’s health. When activated, the effect starts at MinBeatsPerMinute and increases towards MaxBeatsPerMinute as the player’s health gets lower.
Low Health – controls at what health percentage the effect becomes visible 0.3 = 30%
UseCameraPostProcessEffect – enables/disables the low health desaturation effect. You can edit the look of this effect by editing the Post Process Settings in the BP_LowHealthCameraPostProcess Class Defaults.
Material Settings
These settings are found in the M_LowHealthScreenEffect material.
Color – which controls the low health screen effect color.
EdgeThickness – controls how far toward the center of the screen the effect is visible.
Pulse Strength – effects how bright the heart beat effect is.
Max Opacity – controls how transparent the effect is on the screen.
BeatTiming and Strength – are set during gameplay and should not be edited.