Solved
Button on Presentation
On the presentation for the Project item, there is a button. How is this added? Can other buttons be added to presentations?
These two buttons are a feature of the field of type "SI Project" called "Source Project" in the screenshot.
No other type of field offers that, it's built-in and you can't control it. You cannot add buttons to presentation templates.
The only way I've found to approximate adding buttons to a presentation template is to use a rich text field and populate it via trigger with images and hyperlinks.
This works well for the web interface, and not so well for the client. There might be some smart way to do that, maybe others could comment.
I sense this could turn into a product idea.