In case you are only using Jira Software then there is no other level above Epic. However you can still link it to any other issue using links in Jira. If you want to create hierarchies then also take a look at Portfolio for Jira or may be Structure app.
Depending on which folders we are discussing here. For manually created folders, you would have to add a generator (Automation+>Insert>JQL) which will put your epics there. But if we are talking about grouper folders, only manual adjustments can help here. Again, I will need more information before providing more in-depth suggestions.
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