Okay so i have a addon that gives me a google logo i can press to try my search in google if i cant find something on duckduck go but i would like to have the opposite too so a button that would let me click to search on duckduck if googleing isn’t successful eg. If someone sends me a google search link
Swift Selection Search is an extension that adds search engine buttons on selected text.
I don’t think this is exactly what you are looking for, but I guess it has a similar use. I just discovered it last week.
I have looked at it and some similar, but they are non customisable and i don’t like that