Can the tx help at all?
Tx: 371a61ce1262da1de44a9aef2f3bfb9a79f3ae0d25f23255741d18a5bacb0ce9
How can I cause Electrum to forget a transaction?
As the fee you included in your transaction is below the relay amount, you can create another wallet with your master public key and that will have the transaction missing. I don't think Electrum is able to purge transactions yet, as I have seen a lot of users requesting it.
Steps:
1: Export Master Public Keys.
1.1: Go to wallet and click on Master Public Keys.
1.2: Transfer that string of text onto another computer. (If they are on the same network, ssavr.com is an excellent tool to do it.)
2: Create the transaction from another Electrum wallet
2.1: Setup electrum on another computer
2.1.1: "Restore a wallet or import keys"
2.1.2: Standard wallet
2.1.3: Input your Master Public Key.
2.2: Go into settings and enable dynamic fees, if it isn't enabled already
2.3: Create a transaction as you normally would.
2.4: Instead of signing it, click copy.
2.5: Transfer the string of text into your wallet with your private key installed. (Again, if they are on the same network, I recommend ssavr.com)
3: Signing the transaction.
3.1: In your old wallet, click loan transaction -> text
3.2: Paste your string of text into the box.
3.3: Sign the transaction and broadcast it.
If this sounds too complicated, I can do the second steps for you. I will be able to create the transaction, you can examine it and sign it.
You have to send me the Master Public Key. There is a few problems regarding privacy and security. I can tell you more about them, in case you want me to do it.
Edit: If someone is able to come up with a simpler solution, I would like to hear it. I have always done it like this.