Thanks for your answer.
I only use linux and android tablets, so I already know how to transfer files via command line.
The point is, that there is already a function to upload files in webconf, but if sd card is full, you cannot upload anything.
With just a little dropdown to choose between mounted usb stcks and sdcard, you would be able to upload more.
I have a buildin usb sd card reader with 128GB sd, and just 16GB sd as boot.
BR Karl