Thank you very much
So to summarize;
When importing a new private key from cold storage:Use Openledger.io or bitshares.org/wallet to create a new account "Example-Account-Name444"
Under this account, a WALLET is created (you have the option to add more wallets to the same account if you like).
BACK UP this account. Settings > Backup > Backup from brain key.
Write down the 12 brain key words on pen and paper, write 2 copies and store them in 2 separate secure locations. (If your house burns down, you'll be glad of another copy somewhere else)
Go to 'Import Private Key'. The funds from the private key should now show up in this WALLET.
Send ALL FUNDS to yourself. Send funds to "Example-Account-Name444'
Your private key funds, and any future funds that you send to 'Example-Account-Name444' are now secured entirely by your 12 word brain key.
ITS NEVER ADVISABLE to throw away any previously used private keys, but THEORETICALLY you could throw away your now-old cold storage private key because all of the funds are now secured by the brainkey.