public boolean isExisting() {
			return (status == Status.CORE || status == Status.EXTENSION ||
				status == Status.EXTENSION_ERROR || status == Status.EXTENSION_OVERRIDE);
		}
Return true if the element is already installed (not pending)
@return true for an existing extension
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/app/plugin/processors/sleigh/SpecExtensionPanel.java