Electrum, by default, connects to public servers which will not be affected by your Bitcoin Core node. So, whether or not your Bitcoin Core was synced should not make any difference... unless you are connecting your Electrum to your own private Electrum Server (like ElectrumX, electrs or Electrum Personal Server) which is connected to your Bitcoin Core node.

Are you running a private Electrum Server?

Basically, if the private keys in Electrum are the same as the ones in Bitcoin Core and have been imported as the appropriate script type so that the addresses holding coins in Bitcoin Core are the ones being displayed in Electrum... Then everything should work.


It does... The command is dumpwallet

It will allow you to dump ALL the private keys contained in the wallet.dat (including ones in the keypool which are not displayed in the "receiving addresses" list)


That's not how it works... The two wallets, while containing the same keys/addresses, still operate independently of each other.

For instance, it's possible to export a single key out of Bitcoin Core and put that into Electrum, but still have other keys in Bitcoin Core that aren't in Electrum... And vice versa, you could have keys in Electrum that are not in Bitcoin Core.

However, for any private key/address pairs that are in both wallets you should see all the same transactions for those addresses (assuming both wallets are properly synced and up to date).