clearing search history feature: not that I recall. (I would have to look into this as it surely will be stored in a file on disk and one could then nuke that file to Kingdom Come, but that's ... a tad hacky. 😉
I don't expect any performance gain from removing your search history.
At least I haven't seen anything related pop up in the top 50% cost reports when profiling Qiqqa runs in the past. 🤔
Is there a way to clean all of my search history, and does that improve overall performance of the software?