MPLAB X is evolving, and this means that new features are being added at every release. Sadly some old features that have been with us since the early days of MPLAB have gone the way of the dodo.
Animate is one of them. I used it in all my books in the very first chapters, when showing how to use the simulator and mostly in the first simple loops. At the time I was writing the second edition of the Flying PIC24 book (Programming 16-bit microcontrollers in C), it was still available in what was one of the last betas ( beta 7 or 8 ) but it has disappeared shortly after.
I am told there is a simple replacement for it: if you stick a paper clip near the F7 key on your keyboard, you get a very similar result !?
Note for Mac users: You will need a second paperclip to keep the Fn key down as well