Persistent forward and backward buttons and content preview
The software is great, but could you make back and forward buttons (configurable) persistent? I mean, in a way that they do not disappear seconds after a link have been activated. Suppose the situation: I am reading a scientific paper, find a citation, click/tap on it, so I am taken to the reference, I read the reference... and the buttons to back where I were disappeared! So, I have to change the reading "mode" tapping on the upper-right X.
Other improvement in this area would be showing a destination preview when we hold the link of the citation.