First, the search function in
dconf-editor searches only among those things which are directly visible on screen or reachable by scrolling (note that the search field looks just like the one in other applications like Nautilus).
I know of no other graphical tool you could use. So you probably need to use the command line tool
dconf (also from the package
Specifically for search recursively through the whole database (including keys and values) I would use this command:
dconf dump / | grep SEARCH-TERM
dump basically gives you the whole database in an "Windows-Ini-File"-like format. For browsing through the database, use
dconf list /PATH.
As you've mentioned
gsettings, the equivalent search command there is:
gsettings list-recursively | grep SEARCH-TERM
However, this may not be what you want (for a search for
unity, this gives completely different results for me). Not sure what database is used here.
Edit: After reading this question, I noticed that
dconf shows you only the settings which are actually set in the database, not all possible settings like
dconf-editor. Apparently you can use
gsettings list-schemas to give you all possible settings.