Perhaps something has changed then, after all, before without problems you do double spending with a higher Commission and before the first is held and the first is discarded. Truth so was on Bitcoin Core wallet, on Electrum here is only until try to understand as to remove from applications transaction to anew broadcast  another already suppose

Edit: If the initial transaction is marked as replaceable, its inputs can be spent once again to different outputs if the transaction is forgot by your Bitcoin Core wallet (it can be done manually). The built-in "Bump fee" functionality forces users to decrease the change output's value and does not allow to modify other outputs. If the initial transaction is not marked as replaceable then most nodes will reject another transaction as a double-spend attempt.