Open Only mode?

On the top menu bar, click on the gear icon to enter Global Settings. There, you can enable the Open Only mode. It will not close your existing positions when the Master does; it will only open the new ones.

One other option is clicking Copy Settings, COPIER STATUS > OPEN ONLY. It will not copy the closed orders anymore. However, open orders will still be copied. When a StopLoss or TakeProfit already exists while the mode is set to OpenOnly, the StopLoss or TakeProfit will stay active. When a new trade is opened with OpenOnly mode, the StopLoss and/or TakeProfit will not be copied.