Are you getting the Error 100093 or "Transfer timed out" message when trying to transfer a hex file to your micro:bit using MacOS 13? You're not alone. Many users have reported this issue when trying to use the drag-and-drop method to transfer files to their micro:bit. The good news is that the micro:bit team is aware of this bug. You can find information regarding a workaround on micro:bit's support article.
Is your micro:bit disappearing from Files after connecting via WebUSB direct flashing? This is because Chromebooks only allow one method of access to a device. If you would like your micro:bit to show up in Files, you will need to unpair your micro:bit from WebUSB direct flashing. To download your hex file, instead of pairing your micro:bit, you will need to click the three dots and click "Download as file."
Normally downloaded files appear in Downloads, however, there is a way to get your program to download directly to your micro:bit. In a Chrome browser, click the three dots in the top right corner. In settings, click "advanced" and turn on "ask where to save each file" in the download section. You can find a video of this process on this webpage. Every student that logins will need to adjust these settings.
You can find more information on micro:bit's support article.