Currently, the only way to link issues to Epics via the CSV import is to map the "Epic Link" field to the issue key of the Epic.

That being the case, in order to import Epics and linked issues on the same CSV file, we need to manually set an "Issue Key" for the Epics, requiring us to know of a unique "Issue Key" that can be used and making it only possible to achieve this using the External System Import tool, only available to administrators.

It should be possible to either use the same principles available for linking issues - assigning an ID exclusive to that project and linking issues via that value; or allowing the linkage using "Epic Name".