How to edit the "account" in the "transactions" page?

In the “Transactions” page, there’s an “account” column in the right hand side. But when I click the little pen icon to edit the transaction, where’s no place to modify the account. Why is that?

The reason for asking is that somehow I have one transaction deleted. But when I added it back manually, I cannot select the “account”, so the manually added transaction looks from a different bank account than others transactions which are automatically linked. How to fix this problem?

Also, the “transaction” page doesn’t have the running balance. So how can I make sure it matches my bank account?
If I cannot compare the running balance, how do I know if some transactions are accidentally deleted?