Export it as a .reps file first. Deleting takes effect immediately and syncs to your other devices, so an export is what lets you put the material back.
Deleting a class or subject is gated behind a confirmation that names exactly what will go, including how many linked deadlines are attached, so a mistapped button will not cost you a term's work.
Export the subject as a .reps file. That file is a complete copy of the cards along with their photos and drawings, and importing it later brings them back. It does not restore review history, so cards return as new, but the material itself is safe.
Doing this before any significant reorganisation takes a few seconds and is the only backup Reps offers.
The instinct to clear out finished classes is a strong one and often regretted. Material returns: the anatomy from first year turns up in a clinical exam two years later. Export before you delete, and keep the file somewhere.
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