Hi,
No.
Nicolas said, edit the email and copy your content (store it in a local file to not loose it).
Remove the customization, using the "trash" icon. Your modification will be delete and the original file will be restored.
Edit the email once again, you will see the original email content and you can re-put your modification thanks to the file you previously backup.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.