Hi,
I am having issues with the serial port button not always being functional. I have tried having the device plugged in before starting VS Code to use the Particle Workbench, and not to see if I could get the serial port to work. Instead I use the CLI to start the serial port monitor and everything is OK.
The other issue that I have experienced is that when I use external source code from libraries, and go to delete them from the Explorer from within VS Code, then go to compile, I sometimes get compiler issues saying that there is duplicate references to variable names. I have to close VS Code and reopen VS Code to get the modal dialog at the bottom right of the IDE that has the Clean button available. Once I click that then the Compile button, everything works as should.