Not going to recommend editing mirc.ini
[find] has a history of searches in remotes editor, [find2] is a history of searches in channel/status/@window. You can add new searches to force the older ones to expire.
If you don't want a #channel search to appear in this list, you can use /findtext to jump to the line.
https://en.wikichip.org/wiki/mirc/commands/findtext