Hi there,
So Yes, to the first Q’ They are working on one, No other info though at this time 
The second Q, Nrf_dongle. ($9) It is a USB dongle that is programmable. It is used as a BLE endpoint for the computer It can be configured to Scan BLE advertisements and connect to the Xiao running Central or Peripheral code, connected with wire shark it can be a BLE sniffer for Radio testing (transmit power, etc)
here is a thread talking about it also.
Seeed XIAO BLE Sense nRF52840 deep-sleep mode - #21 by Vint1k
The Xiao comes preloaded with the Adafruit UF2 bootloader, which is designed primarily for drag‐and‐drop updates of the application firmware over USB. In this mode, when you double‐press the reset button, the board enters DFU/UF2 mode and appears as a USB drive, allowing you to copy a UF2 file to update your app.
When it comes to updating or replacing the bootloader itself (for example, switching it out for MCUboot), things get a bit more complicated:
- Bootloader Update vs. Application Update:
The UF2 bootloader on the Xiao is mainly intended to update the application area and is typically locked down to protect the bootloader region from accidental overwrites. In other words, it’s not generally set up to allow self‐updating of the bootloader via the drag‐and‐drop UF2 process. - Reflashing MCUboot:
To replace the existing Adafruit bootloader with MCUboot over USB, you’d need a UF2 file that’s properly formatted for a bootloader update—and the bootloader region must be writeable via DFU mode. Unfortunately, the standard Adafruit bootloader doesn’t usually support reflashing the bootloader region itself over USB. In most cases, updating the bootloader (i.e., replacing it with MCUboot) would require a dedicated programming tool (like a J-Link or another SWD programmer) or a specialized DFU mode that explicitly allows bootloader updates. - Risk and Recovery:
Even if there were a method to update the bootloader over USB, doing so is riskier than updating the application. A failed bootloader update can “brick” the board, which is why most boards—like the Xiao—lock the bootloader region against accidental updates via the USB drag‐and‐drop method.
The Adafruit bootloader on the Xiao is designed for application updates over USB and does not natively support updating (or replacing) itself with MCUboot over the USB DFU mode that presents a drive in Windows File Explorer. It would be the right thing to allow but Adafruit doesn’t want that! so much for openness, To flash MCUboot onto the Xiao, you need to use an external programmer or a specialized DFU procedure that’s not part of the standard user experience.
HTH
GL 
PJ 