I asked the same question from myself and it took some time to find a proper solution.
KDE config settings stored in ~/.share/config and klippers' in ~/.share/config/klipperrc
In that file there is configuration group called Notification Messages in which all answers which were answered with "Do not ask again" checkbox ticked are stored.
[Notification Messages]
really_clear_history=false
In this case whenever user clicks on Clear Clipboard History it will always taken as if the user got the pop and answered no. If it were really_clear_history=true then it would clear history without asking confirmation from the user.
So if you want to restore defaults, simply remove the whole block or just the key value pair for which you want to restore the defaults for.
Posted by Bonyiii to Bonyiii's deck (2017-11-01 12:56)