The quick & easy way is to make a Custom Filter is to use the clipboard.
- Select the person in the People view
- Edit menu → copy
the clipboard dialog automatically opens if it wasn’t open already - select the Person on the Clipboard
- right-click the Person to pop up the context menu
5) choose the * Create Filter from the [RECORD TYPE] selected menu item
6) give the new filter a memorable name
Now you can just use that custom filter in the Person Filter when you do your normal Export to GEDCOM.