Apparently, by checking the Replace by fee option in the Electrum Preferences, you can basically double-spend a stuck transaction. However, outputs cannot be changed, only the fee.
I thought Electrum did also allow you to change the outputs before signing & broadcasting the second tx, but apparently it does not.
You can disconnect Electrum, remove the unconfirmed RBF-transaction, create a new one (from same UTXOs), save it and finally broadcast it to the network.
thanks for reply to all.
can you please detail more this step by step?
thanks in advance