A long-awaited improvement ...
You can now export a GEDCOM that starts with an individual. That is, rather than exporting a file that includes everyone in your Watchlist -- which could be very large -- you can now export one individual's tree.
The usual privacy restrictions apply. You have to be on the starting individual's Trusted List. If you're not on any of their family members' Trusted Lists, what's exported will depend on their Privacy Level.