I have just bought the 3.5 upgrade (from 3). It seems to want to install a new version of Dorico on my machine and not upgrade the old version. Is that correct? If so, can I port all of my own shortcuts and tweaks from the old version to the new version?
That is correct. The first time you run Dorico 3.5 all your stuff should port automatically. It may be that it happens on closing 3.5 for the first time; I can’t remember - so if your shortcuts don’t work immediately, close 3.5 completely and then launch it again.