What is a “sub-wallet” in this context?
Discussion
You can create as many sub-wallets as you want under the same node. For example you want to give a family member a custodial lighting wallet on your node, you won’t give them access to the nodes funds.
And that’s how you should treat your self as well. It’s like separating your self from your node.
You can use the LNDHub for that.
LNDHub and LNBits are account systems that can use LND as source of funds. By using an account you may have another layer of recordkeeping, but its still the same hotwallet