Quote from: alexeyneu on Today at 01:12:43 AM

these pubkeys may only have something to do with redeemscript (which you'll not have with electrum anyway). anyone who knows private key and wallet address(which you wont know from that private key) can do createrawtx , signrawtx , then broadcast it .

https://bitcoin.stackexchange.com/a/51366

The redeem script may not be displayed in Electrum,
but the information to produce it on demand is saved in the wallet file since it's required to be included to the signed raw transaction.
A client/wallet will not be able to sign by having only the private key of a single signer without the redeem script or cosigner's public key to reproduce it.

In the link's instructions, the redeem script is saved in the wallet after using "addmultisigaddress" command.
That enables it to sign using "signrawtx" without adding the redeem script, otherwise (if the wallet just contains the private key via importprivkey), it will fail to sign.

The key point is written in the "Details" part below that post.