UIBackgroundBlur
Use it on ScreenSpaceUI or World Space LGUI Renderer.May have some issue when MSAA is on. This component can make blur effect on background view's image, it is just like UMG's BackgroundBlur. 
Create it by select "Create UI Post Process"->"UIBackgroundBlur": 
| Property: | Function: |
|---|---|
| Blur Strength | Blur effect strength. |
| Apply Alpha to Blur | Will alpha affect blur strength? If true, then 0 alpha means 0 blur strength, and 1 alpha means full blur strength. So if you need animation on Blur Strength, just use "Alpha To" node on blueprint. |
| Strength Texture | Use strengthTexture's red channel to control blur strength, 0-no blur, 1-full blur. |
| MaskTexture | Use maskTexture's red channel to mask out blur result. |
| Custem UIMaterial is not supported. |