private String getExtLibName() {
		String extLibName = null;
		if (extLibNameComboBox != null) {
			extLibName = extLibNameComboBox.getText();
			if (extLibName != null) {
				extLibName = extLibName.trim();
			}
		}
		return extLibName;
	}
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