Hi,
first of all, having 2 configurations won't solve your problem. As mentioned in the training, configurations are used for different "power modes" of the USB device. What you need is to have 1 device descriptor, 1 configuration descriptor and 2 interface descriptors (assuming you are going the "composite device way").
If you are using ST Middleware, you need to change interface descriptors in usbd_hid.c file, and also other functions, e. g. for reporting and enumeration of the device.
BR,
Jaroslav
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