Yes. A custom asset holds anything without a daily quote: unlisted shares, a pension pot, a private fund, a car, a collection.
You give it a name, a category, a currency and a quantity, then add a valuation whenever you have a better one. The most recent valuation is what the portfolio uses, and the earlier ones stay as its history.
On the free plan they take no room among the ten share holdings. They use one of the five bond, cash or custom holdings instead.
See what else the account holds