Most recent web browsers have some kind of "private browsing" functionality, where no history is recorded, and temporary files are deleted when you close the browser. Such a mode would also be useful for Gwenview, for... y'know... *cough cough* Reproducible: Always
There actually is: Settings > Configure Gwenview > Advanced > History. However, it seems to be half broken. Marking this as a duplicate of that bug that tracks fixing it: https://bugs.kde.org/show_bug.cgi?id=332853 *** This bug has been marked as a duplicate of bug 332853 ***