Currently, jmp.chat does not offer a way to re download eSIMs, although they will transfer the remaining data of your old eSIM to a new one if you purchase new eSIM. Despite this limitation, there is a workaround to transfer your eSIM and also re-register it on the same device if it has been erased.
When you register for an eSIM with jmp.chat, you will receive a code that begins with LPA:1$, along with a QR code. It's essential to take note of this code and keep it in a safe place.
Although jmp.chat claims that you cannot re download eSIMs, you can reuse this code to re-register the same eSIM on different devices or even on the same device if it has been erased. If you switch devices or need to re-register on the same device, while adding the eSIM, click on "Try these troubleshooting steps" on the QR code scanning screen and then enter the code you saved that starts with LPA:1$. This allows you to reactivate your eSIM without needing to request a new one and incur additional charges.
Hope this helps someone!