I also find "open new incognito tab" actions or "take rectangular region screenshot" when I search for the right term.
What's a bit amsing is that searching for "tab" (German localization) finds "LibreOffice DaTABase" as topmost result (the LibreOffice welcome thing has all the LibreOffice apps as additional actions, in addition to the separate launcher entries) with Chrome and KCharselect as next results
Since I cannot really query for the actions directly, I wanted to at least limit it to services that have Actions but KServiceTypeTrader doesn't the "Actions" key apparently