System
MacBook (Retina, 12-inch, 2017)
MacOS 10.15.7 (Catalina), 12
Pro IDE Version 0.1.2 (0.1.2)
Adafruit Trinket M0

I can get the IDE to properly compile my sketch AND transfer correctly to the Trinket, but after transfer it loses the port setting and requires I manually redefine the port setting again in the "select other board & port" dropdown. Additionally, it appears to recognize the Trinket incorrectly as an "Adafruit pIRKey" as this entry is always associated with the correct USB port and I never added it. If I manually specify the Trinket and USB port, it works once, but then the Trinket loses the port and the pIRKey definition remains. Also, it never persists my Trinket setting (regardless of port) once I close the IDE. The behavior seems to be that it insists on seeing the board as a pIRKey, but that's just a guess on my part.

I'm not sure if this has anything to do with it, but I've noticed on my Mac that once the sketch is installed and the board resets, the USB connection temporarily disconnects and reconnects. And I get the red X in the board combobox at the top of the screen. Perhaps this temporary disconnect is confusing the board settings?

QUESTION: Is there any way to remove boards from the board/port dropdown once they have been associated?

Also, FWIW, the standard IDE does just fine with the same sketch and persists settings correctly and recovers from the temporary board disconnect.

To Reproduce
Steps to reproduce the behavior:

1. Install IDE, Trinket support (per Adafruit instructions), and required sketch libraries.
2. Plug in Trinket.
3. Observe that board settings automatically pick up an entry for pIRKey with the correct port we need for the Trinket
4. Manually select the build for the Trinket M0 and correct board.
5. Compile and upload successfully.
6. Immediately loses the port setting and won't upload correctly until you repeat IDE launches - the editor opens, but nothing is happening but the "loading" circle in the middle arduino-pro-ide#4
7. Close IDE, reopen and it's as if the Trinket was never there.

Expected behavior
Trinket and port settings should persist like the standard IDE