Every new add-on or browser extension you install in your Tor browser weakens its ability to keep you safe and anonymous online. The Tor browser was not designed with extensions and additional software in mind, so while you can indeed add them if you want, how they will interact with Tor is unpredictable, and the chances are that they will end up beating the purpose of Tor itself, which is anonymity and security. Also, if you customize your browser, you'll create a more distinctive "browsing fingertip" for the servers you visit. That alone will make it pointless to use Tor because if your fingerprint is unique enough, you will become identifiable even through Tor.