Is it possible to use the cash flow planner with multi-currency functionality enabled?

It isn't possible to use those two features together, Patrizia.

Enabling Multi-currency permanently changes how QuickBooks Online processes transactions. Additionally, the cash flow planner chart doesn't include multicurrency-enabled files.

You can visit our Cash Flow Planner FAQs guide to learn more information, especially how forecasting works and what data is included.

Please let us know if you need any further assistance.