Have a "highlighting" mobile mode rather than text-select
Long-pressing and then dragging the text-select is rather cumbersome and time consuming. If there were a highlight mode that could be turned on and any finger swipe would create a highlight, that would speed up mobile highlighting.
This small change would make a world of difference for annotating on an iPad. Virtually all other PDF and note-taking applications have some basic pen and highlighting tools that can be activated from a toolbar at the top.
The tediousness of the present set-up has led me to do much of my annotating outside of Mendeley (in PDF Expert). I then have to reimport the PDF back into Mendeley via the Desktop app.