Instead, see "Sitemod.io" by the same developer. (By the way, Sitemod.io Chrome extension is not allowed by Chrome anymore. But Sitemod.io Firefox extension works - somewhat.)

However, "Permanent Inspect Element" doesn't seem to do anything. The toolbar button only has three buttons: "Save page", "Reset", "Reset all" - and doing nothing.

Even while saving, and refreshing, nothing!