Xavier I thought you had to do that only the first time. Taking the SD card out of the unit with the steel enclosure is a problem. You have to cut off halve of the SD card cover and mount it int he SD card slot under the TFT in order to assemble the case.
Than you have problem 1 (no grip on the card anymore. Secondly there is no SD card slot in the metal housing. So I would like to have a way to write data on the SD card without removing from the cardslot on the TFT.
The case is designed and sold by Van Daal Electronics, not by me
The 3D printed case i designed have a SD card slot.
But you should be able to to access the SD card from your computer without removing the SD card if you have bootloader 1.07.
Once in the bootloader, press "Button 3 : SD card access".
You have to be patient, after 20 seconds, your SD card will show up on your computer and you can copy the firmware on it.
Then unmount on your computer and press Exit.