The window glass is nice when it's clean.  Is there anything I can put on it so it cleans easier?  Rain-x or maybe smoke-x?  Do you even clean yours or how often do you clean it? What do you suggest to make cleaning easier?

I have never understood glass and cooking when the glass is going to be exposed to fatty heat! Clean after each use would be my only suggestion!

 I am with Bent on the why.

 The glass may not be glass. It could be ceramic as in a gas or wood fireplace or stove. 

 As far as I know there isn't anything that would work to retard accumulation.

 What you may want to try is a cleaner expressly made for fireplace or stove glass. Once used, subsequent cleanings tend to require less effort assuming the cleaning is frequent

I will chime in.
Why they would put glass on any type of grill is beyond me. The pit boss vertical glass is useless, thinking it has to be a “selling point”.
Our pellet stove glass is cleaned every 2 days or so and the etching is obvious to some degree.
With meat, grease, liquids etc. I have to say that attempts are futile in that environment.
Just my 2 cents.

Let it go long enough and you will no longer notice it has glass, and maybe then it will not bother you!