There is a setting in TWS/IBG->Config->API -> Include Virtual FX positions when sending a portfolio".

https://www.interactivebrokers.com/...g/fx_portfolio_-_virtual_fx_position.htm

When checked, positions returned by reqPositions and similar requests will include Virtual FX positions, i.e. "positions opened in currency pairs" rather than just net cash currency balances.
So, this info is available via API.