Import bitcoin core generated multisig public address to electrum multisig wallet for watch(2/3) and sign(1/3) I have 3 Machines, and I want to create (2/3)multisig wallet. Sign with other machines safely.

I have;
xpub1, xpub2, xpub3
xpriv1, xpriv2, xpriv3

Machine-1: In electrum:
New/restore->Multisig Wallet->Use a master key->2/3->Cosigner1: xpriv1, cosigner2: xpub2, cosigner3: xpub3,
for watching (2/3)multisig wallet and partially sign(1/3).

How to import machine-2 generated public addresses to Machine-1 for watch(2/3) and partially sign(1/3)?

The electrum wallet database is look like json formatted. Am I need manually enter there(json["addresses"-&gt;"receiving"]) or any other way to import a corresponded addresses
As you were told on bitcoin talk forum you can't import arbitrary private or public keys and create a multisig setup with them using electrum. It only supports using extended private and public keys or seed words for this functionality.

If you just want to create a watch only wallet with the address itself then you can do that. Go to file > new/restore, enter a unique filename and click next and when asked what type of wallet you want to create choose the option to "import bitcoin addresses or private keys". Then paste in the address in the next step and proceed with on-screen instructions for the rest. This will let you watch transactions relevant to this address but you won't be able to sign any outgoing transactions.