Update. Heres how Im now able to restore connection when UIFLow fails to pro and continue development.
red power switch on M5Stack Core S3 to Off.
unplug USB cable from computer
red power switch on M5Stack Core S3 to On.
press and release button on leftside of M5StackCore S3. Wait10s , let it poweron and go to UIFLow or run last program
plug USB back into computer. For me the UIFLow2 device on screen now goes green 90% of time, but even if it doesnt continue.
Select Run or Download to continue development.
If the above doesnt work, I persevere with the M5Burner application set to CoreS3 to erase firmware and reload the UIFlow firmware. If its configurator screen shows the correct serial port you are likely to succeed with the above procedure (mine would flip between 2 serial ports).