Edit Theme Codes

Hi Everyone,

I am trying to change some Codes on my WordPress theme with the help of Editor, I need to add some Google Analytics Tracking codes as well. But every time I try to change, it is showing me an error called ” Not Supported” and the process is incomplete. For the same, i need to download a plugin which takes my disk space.

Is this is an error by WordPress or do I need to change some settings to edit any kind of code in my theme with the help of the editor.

Looking forward to your reply.
Thanks