I'm sorry you have been desapointed by this, may be I haven't been enough explicit in the description : "Was formerly "Konquefox" extension : but due to limitations of the new WebExtension API system, the "Clear URL" button doesn't work well on some versions of Firefox. We're hoping that to be improved in the future !"

I'm checking every week to see if there are some improvments in the WebExtension API, it's all that I can do.