I just went through transition at work after about 9 months of HRT. My breasts were not so obvious under my usual uniform of polo shirts/slacks, even without any attempted concealment. I elected to go public more because I had already changed my identity documents and was just waiting to get into a situation requiring producing my documents, such as for company travel or such things.
I work in a Fortune 500 company in California, so besides local and state legal protections I had the benefit of a supportive corporate structure. But even given all of that, I have been pleasantly surprised at the smoothness and ease of the transition. Everyone has been generally supportive, including leadership all the way up, and a few people, including my immediate boss, have been very actively using my correct pronouns in demonstrative fashions, and correcting the occasional misgendering that's going to happen.
I don't know what your specific employment situation is, but I'm working with some of these folks for 10-20 years, and they're all taking it in stride. I'm really glad I did it now, and will be able to cite working here under my legal name going forward. Meanwhile, I'm enjoying every day, and even wore a dress and boots to work today, first time ever!
Erin