Question regarding importing .txt formatted documents

I have content that I’d like to import into LingQ as an eBook. I would like LingQ to split the file up at specific points. Is there any specific “marker” I should put into the file in order to tell LingQ where to split the text as a given lesson?

I think the only way is to split the text into separate portions and to import each portion as a lesson.

I’ve copied and pasted chapters into lessons before, one lesson per chapter, all chapter-lessons in one book-sized course. It never occurred to me before to save each chapter to a separate file for import. That would work also, and may have some advantages. But in either case, it’s a manual operation.