private boolean validLibName() {
		String extLibName = getExtLibName();
		if (extLibName == null || extLibName.length() == 0) {
			showInputErr("An external library 'Name' must be specified.");
			return false;
		}
		return true;
	}
Pop up the data tree dialog so the user can choose the external program.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/symboltree/EditExternalLocationPanel.java