It is very convenient because you delete the cache and update the page by clicking the icon. There are also requests, there are times when the notification that appears after icon clicking is in the way. I want you to be able to hide this.
Also, I confirmed that the Empty Cache Button icon will disappear from the combination of Firefox 55.0.3(x64) and Empty Cache Button 3.4. It will be displayed when you return to the previous version.