How do I reactivate a to-do I already pushed?

Reactivating is done on the Supernote device itself: drag the to-do out of its "Synced ✓" area on the device. After it syncs back, it shows up here as a normal, editable to-do again — marked with a small "already pushed" badge so it isn't sent a second time. You can't reactivate it from inside this desktop app.