No you don't.
You just mark the transaction you just wrote, so that you see all it's content in the add/edit fields. Then you just change whatever you want to change (as in this case the payee, and sum) and click "Add".
This is how you re-use EVERY transaction you write without having to...
Well, it is still an Asset. Just as any other promissory note.
And just as for the other accounts in Portfolio the value is uncertain until you cash it in.
Why are you asking for a new _type_ of account when what you want is in fact an account (that you can add yourself) within one of the asset types? (Preferably in Portfolio, I think.)
If you check out Accounts that is where they have placed it.
:-)