no photo or drawing?

I'd typically keep it away from the glass enough to clean. 3-6"

"floating shower bench"

There's a joke in there somewhere.

We need pics of youridea in yoyr spa e. IMO a bench that can be removed is my choice always in a shower. Like niches , builit benches are often a sorce of leaks so I do neither .

You need to ask your experienced tile professional. He/she will know the correct brackets to use + how it would be installed up against the glass (or if it shouldn't be). There would have to be some sealant used the never failed in order to make sure that no water ever penetrated between the side of the bench and the glass (if it did, it would look terrible + I assume be difficult to clean out before resealing). I don't know why you would have it actually against the glass - the glass isn't going to help support the bench.

I have seen many floating benches that only are supported using one side + the back wall. I've also seen a few where the floating bench was only supported on the back wall - it didn't touch either side wall.

I was considering having a floating bench installed in one of my showers - I decided to purchase a nice teak bench instead. Below are photos that I saved when I was deciding whether to add one or not:

This one is very close to touching the glass - but there is a space between the bench and the glass:

Below is an example of a bench that is only supported by using brackets in the back wall:

This one hasn't had the glass installed yet - but tile professional said that the glass would come out past the bench. What's interesting about this shower is that the linear drain is "hidden" on the floor along the wall with the mixing valve. If you look closely, you can barely see a line running through the slate tile installed along the edge of the right wall:

A floating bench is pretty complicated structurally. I'd have one supported by two side walls.

Who is getting on their hands and knees to scrub underneath that?