Quote from: Ppppp on November 10, 2021, 04:14:55 PM

-snip-
Is there a way to do it properly ?

I could export the private keys from the old wallet (which is mostly empty) but not from the new one.

Then it's good, you can import the funded address(es)' private keys to the new wallet to spend its UTXOs together with the other wallet.
You already know to to export, yes?

Now, to be able to import keys in Armory, you have to be in "Advanced" or "Expert" mode (Menu: User->Advanced/Expert, then restart to switch),
Then you can now import individual keys to a wallet by double-clicking the wallet name and select: "Import/Sweep Private Keys".
Make sure to select "Import these addresses to your wallet" and not sweep because it will immediately create a txn that'll spend its funds and send it to that wallet.