A derived transaction portfolio is an exact replica of its parent at the moment it is created. The derived portfolio inherits:
Every transaction
Every portfolio property
Portfolio settings such as the accounting method, amortisation method, transaction type scope, list of sub-holding keys and so on.
A derived portfolio continues to inherit all subsequent changes until such time as you directly edit the derived portfolio itself.
If you do this (for example, by changing a particular transaction or choosing a different accounting method), then the link between the two portfolios for that attribute is now broken. Subsequent changes made to the parent are not inherited.
Transactions
If you directly edit a particular transaction in a derived portfolio then the link to the original transaction in the parent is broken, and subsequent changes are not inherited. This can be a change to any field, Transaction property, or cancelling the transaction itself.
Once broken, it is not possible to reinstate the link between the two transactions. In summary:
A derived portfolio inherits all transactions from the parent portfolio at the moment it is created:

You can add new transactions to the parent portfolio and they are automatically synced to the derived portfolio:

You can add new transactions to the derived portfolio but they are NOT synced back to the parent portfolio:

You can update an existing transaction in the parent portfolio and the change is synced to the same transaction in the derived portfolio:

You can update an existing transaction in the derived portfolio but the change is NOT synced back to the same transaction in the parent portfolio:

Furthermore, the link between the two portfolios for this transaction is now broken; subsequent changes to the transaction in the parent portfolio are NO LONGER synced to the derived portfolio:

Portfolio properties
If you edit a particular Portfolio property in a derived portfolio then the link to the original property in the parent is broken and subsequent changes are not inherited.
It is possible to reinstate the link between the two properties by explicitly nulling the value in the derived portfolio. In summary:
A derived portfolio inherits all properties from the parent portfolio at the moment it is created:

You can add new properties to the parent portfolio and they are automatically synced to the derived portfolio:

You can add new properties to the derived portfolio but they are NOT synced back to the parent portfolio:

You can edit an existing property in the parent portfolio and the change is synced to the derived portfolio:

You can edit an existing property in the derived portfolio but the change is NOT synced back to the parent portfolio:

Furthermore, the link between the portfolios for this property is now broken; subsequent changes to the property in the parent portfolio are NO LONGER synced to the derived portfolio:

However, you can reinstate the link by explicitly nulling the value in the derived portfolio'; subsequent changes to this property in the parent portfolio are inherited again:
