The linked question allowed me to do just what I want, but I find it counter intuitive. The help says :
Clear Selection First
Controls, whether the existing selection should be cleared first.
So, checking this should uncheck my selection, and since also "Act on current selection only" is checked, I would believe my selection applies on nothing. Maybe some rephrasing of the option should be done?
Or maybe when "Act on current selection only" is checked, maybe "Clear selection first" should be grayed out, with it checked so that it works as expected?
Or did I miss something?