Hi, Wondering how I can import the wallet.dat file from bitcoin-qt client to Electrum wallet offline. I would like to keep my current bitcoin-qt wallet offline and be able to do transactions from my offline computer to my online computer using Electrum.
You can also import the wallet.dat directly into Electrum. Bitcoin Core needs to download the whole chain (as you mentioned) so that'll take a while. Without the chain, your transaction are indeed illegal/conflicted.