but I was just using Electrum as low fee testing wallet, not Bitcoin Core
1. Electrum also has a terminal, and from command line, similar things should be possible.
2. You can export the private key from Electrum to Bitcoin Core, and complete it, even without downloading the blockchain. The only missing part in my example is the private key. If you verify, that everything is correct, then you can safely complete it, also because the risk of losing coins is quite low, because of low amounts.
Edit:
Has anyone succeeded in doing this?
Yes, see:
https://mempool.space/tx/49b046366f78ce63014646ba86fe2b2959a4442d6df8c0df603c3821493d7f9d
