I have set the Save and Autosave folders in preferences to folders I like.
Dorico 4 is saving to those folders.
However, at every Autosave interval, Dorico also gives me an error message stating that it cannot find the Autosave folder which shows me a path to different computer (which I also use for Dorico 4).
How can I get rid of this error message?
Presumably you copied the user folder from one computer to the other, in order to transfer keyboard shortcuts, preferences etc.
Go into that folder (~/Library/Application Support/Steinberg/Dorico 4/ on mac or %appdata%\Steinberg\Dorico 4 on Windows), open preferences.xml, scroll to line 156 and replace the Autosave path with the correct user account name.