Good question. I've waited until now so I could give a proper answer.
- after-reading-external-file
- before-writing-external-file
A plugin or script could register these handlers.
You could also use two other event handlers:
- save1 (before saving a .leo file)
- save 2 (after)
Finally, you might find these handlers useful:
- command1 (before executing any Leo command)
- command2 (after)
HTH. Please feel free to ask other questions.
Edward