Is there a page on the website or section of the user agreements that will put my mind at ease about this? I’d like to feel secure in knowing that my work belongs to me, regardless of the tools I use to produce it.
You, the author, have the copyright to your work, of course! You can find this information in the EULA under Section 9.
This is a catchall phrasing in case you should upload anything to our website, including the Community. For example, you could post a video clip publicly in the Community, then we would need to work with that data to be able to provide our service.
Key is: “when you access and use the Website”. We don’t have access to anything on your computer, only what you actually transmit to our website / services.