@complecz Hello, thank you for your question. You can have your isolines activated with forecasting maps (wind, precipitation, clouds etc.) - use the section in the Settings of the app "Start-up layer and location" > "Use last overlay", "Use last location". Just be sure to have your isolines activated before closing Windy app. This settings will not work with real-time data maps (radar and satellite).
Have a nice day, Niki