When I purchased my Chromebook a few years ago, one of the first things I realized at the time was that I had no idea how to type special characters with it, such as the registered trademark symbol (®).
I did a bit of research, and I discovered that the trick is using the Unicode for each character. Just type Ctrl+Shift+u at the same time, release them, type in the 4‑character unicode, then press the space bar.
So for the registered trademark symbol (®), for example, type Ctrl+Shift+u at the same time, release them, type 00AE (the 4‑character unicode for the registered trademark symbol), then press the space bar.
Check out my article on how to type common special characters on a Chromebook. Use a Mac or a PC? I got you covered there, too.