A motorcycle shop might be intimidated by it since it is all electrical. But you could try and see what happens. I don't think it is a zero problem.
If the light wasn't on and the fuse was good and the light was good it might be a zero problem .... but given how the bike is wired nothing else would be on either
The voltages involved are ~13v DC and you could actually do step 3 without the bike being on if you wanted to jump right into testing. It would only require a simple multi-meter with a continuity tester (tone tester) to perform.
My best guess is the left control is likely at fault. I can't see how the power would always be on any other way. Keep in mind you have TWO high beam controls on your left control. Ones is for flashing to pass and at the front and the other is the toggle switch on the back. One or the other or both could be bad. Make sure your front flash to pass button is "free" though as it might have got stuck in the downward position.
If you are not willing to take it to a shop I could make a youtube video for you to show you how and what to check. But that might not happen today / tomorrow.