[Keychain] copy from "Local Items" to a "Custom Keychain" throws up an error

I am trying to copy a keychain item from "Local Items" to a custom keychain I've created:

1. Open Keychain app
2. Find the item I need to copy in the "Local Items" list (kind: Web form password)
3. Select the item and press cmd+c
4. Switch to a custom keychain I've created
5. Press cmd+v
6. A dialog pops up, "Keychain Access wants to use the "Local Items" keychain. Please enter the keychain password:"
7. I enter my account password, click "ok" (also tried icloud password with the same outcome)
8. Error pops up: "An error has occurred. Unable to add an item to the current keychain. One or more parameters passed to a function were not valid."

What am I doing wrong, why it does not work, and how to make this work? I need to copy a few dozens of items and copying each item one-by-one is just insane.