Hello @ebunge ,
I tried with an OpenWidow approach("https://coda.io, “_self”) but it doesn’t work, so I’ll have to check with a formula expert 
to see if it’s possible.
However, while searching on the forum, I came across an article that refers to this (How to use a button to go to a page within a doc - #6 by cnr)
Hopefully this will help you to see more clearly.
Sincerely
Thierry