Please follow the steps below (Reminder: This operation can only be performed on devices in the same room):

1. Enter the APP main page, long press the group device you want to modify;

2. Select "Group Information" in the pop-up menu at the bottom of the page to enter the "Group Settings" page, and click "Group management";
 

3. On the other devices list，click the "+" on the right side of the corresponding device name to add, the device will be moved to the current grouped device, and then click "Save";
 

4. After the saving is successful, go back to the main page of the APP，and try to click the group switch button to test whether the added device can be controlled; if it cannot be controlled, it means adding the device fails and it needs to be added again.