Need a close up of the leaves to be sure what it is - at the moment, I'm guessing possibly a Pittosporum, or maybe some kind of holly, but really need a better picture of the leaves.
That said, however, I don't know who's responsible for the planting outside your office window, but you should speak to whoever it is and strongly suggest they remove the plant, because when something gets to that size and completely covers a window,it's a case of wrong plant, wrong place. If it's left in situ, it will soon cause a problem in the room above, where exactly the same thing is starting to happen, its already covering the bottom quarter of that window. Any replanting subsequent to removal should preferably be with something that doesn't get above windowsill height.
There isn't anything 'unobvious' you can do otherwise - if you cut it right down, people will notice; if you selectively cut out some branches, everyone will notice that too, but it's not reasonable to allow a plant to completely cover a window - should any repainting or repairs be necessary, the plant would have to be cut down anyway to allow access. By the looks of it, it must already be covering the downpipe from the guttering, and presumably the drain at the bottom - I'm surprised the owners of the building haven't done anything about it, not least because of its proximity to the building's foundations. Identifying it would mean you'd have some idea of just how tall its going to get - and how deep and wide the root spread may eventually be (though it must be fairly big already), so please add a photo showing a branch and leaves.
There are methods for killing stumps, but they're not particularly effective without cutting the tree/shrub down first.