It’s doesn’t insert the search prefix automatically, but you could use this script as a toolbar script.
If you put the toolbar script’s icon next to the search field it’s just a little mouse movement and one click.
-- Insert search prefix
property theSearchPrefix : "name:"
tell application id "DNtp"
try
set theWindow to viewer window 1
set theQuery to search query of theWindow
try
if theQuery does not start with theSearchPrefix then
set search query of theWindow to theSearchPrefix & theQuery
end if
on error
set search query of theWindow to theSearchPrefix
end try
on error error_message number error_number
if the error_number is not -128 then display alert "DEVONthink" message error_message as warning
return
end try
end tell