Recently started to do merges for Qt Project again, there are some mergers, then perhaps there are some duplicate work. Better to find them before creating new merges.

jkt in #gerrit channel on irc.freenode.net answered my question, “message” is for it.

Documentation in Gerrit Doc: Gerrit Code Review – Searching Changes.

For me, I could just try “message:”Merge remote-tracking branch””.