Thanks for posting in the Lucidchart Community! I'm sorry for the trouble, but I am happy to help. If you are importing data to create your org chart, then you will be asked during the import flow if you want to separate your org chart by department. This would be the easiest way to separate your org chart. If you did not import data to create your org chart, then you can export your org chart as a CSV (as shown in the screenshot) and then import that CSV. You may also benefit from our Group View feature, which is explained here.
Feel free to let me know if you have additional questions.