PS
I am using Electrum on Tails without persistence, but I did make a backup (Files -> Save backup -> Backup Directory)
About the signed message that others have suggested; there's no standard way to do it yet.
So if you decided to use your Electrum and it's not an old legacy wallet with '1' addresses, you should include a note stating that it's signed with Electrum.
Otherwise, the recipient might use an incompatible client or message verification tool and fail to verify your message.
For example: "
This was signed with Electrum and must be verified using Electrum or other compatible clients/tools"
What is the problem with legacy addresses starting with 1 and why can't Electrum sign them, and how can it be solved? Which old version of Electrum should we use if we have such addresses?