If your transaction includes a UTXO assosiated with the 21st address, the gap limit is 20 and you haven't generated more addresses, your cold wallet can't sign the transaction?
Correct me if I am wrong please.
As I mentioned in the last part, I've tested that before posting.
I tried it with a UTXO associated with "
red-highlighted" 120th address (
index 119) of the online watch-only wallet and the offline Electrum can still sign it.
If you parse the PSBT, you'll find details of how to find the correct private key.
Can confirm. Works exactly as described. Started electrum in offline mode, restored from seed, and signed a transaction from an address way past the first 20 addresses shown. The "Sign" button is active as soon as I load the transaction in the offline wallet, so presumably the distance from the masterkey is inside the psbt somewhere. This is really great. If I can remember the 12 word seed, I never have to have a secret wallet file existing anywhere and I can transact to my hearts content. Probably makes sense to chisel that seed on a rock and bury it in the north 40 somewhere, in case I forget it.
Thanks for dropping the little suggesting to parse the PSBT. Looks like gibberish in there so that gives me something to figure out next! I didn't even know about "testnet" until your post yesterday, and now I've got sucked into that fiddling with all the electrum features at the low, low cost of zero. A great way to learn how bitcoin works from a users perspective.