For this, we add the Blur Widget with our simplified menu, using the Blur Strength value to determine the strength of background blur being applied.
On our Menu Widget Blueprint's Graph, we create a script to handle how our menu reacts to button clicks.
Above, when we construct the widget, we are turning on the Mouse Cursor. When the Resume button is pressed, we hide the cursor, un-pause the game, and remove the menu from being displayed.
When the Quit button is pressed, we quit the game. Inside of our player character's Blueprint (see below), we add a script to create and display the menu when a key is pressed. In this case, whenever P is pressed, the game is paused when the menu is displayed.
The result is the ability to pause the game and blur the background, keeping our menu intact for players to interact with.
We could also decrease the Blur Strength from 50 (above) down to 10 (below) to make the background slightly more visible.