I agree with @DBear,
But as an example to explore, using one of my hype Image Gallery examples.
This edited version shows an idea of how to get the blurring.
The idea is to place an empty group between the gallery and all the other elements you want to blur.
Then set the empty group to fill the scene and it’s back drop filter to blur.
The Blur group and the image gallery group are set be hidden at the start and the show when the thumb is clicked.
This is only a quick example to give you an idea…
slideGalleryWithBlur.hype.zip ( note that I removed a lot of the original code so the gallery in this example probably does not work fully as it should, the example is as I say to show the blur idea )