Investments in Manager work exactly like multi-currency accounts. They are revaluated based on the market price. And the difference between the real balance and revaluated balance is posted to Investment gains (losses) account.
Now, this account will typically represent both realized and unrealized gains (losses).
To get realized gains figure, you can go to Reports tab and generate Realized investment gains (losses) report.
This report can be suplementary report to your profit & loss statement to show the portion of your investment gains that has been realized. Or you can make a journal entry to transfer realized gains into its own account on profit & loss statement.
The concept is exactly the same as with foreign currency accounts.