I've finished with the first round of the "Go Back" Button.
The "Go Back" Button allows you to delete your last entry, without having to start completely over.
Although I have it working, there are some limitations:
1> I removed Spacing
2> The color coded dots on the fretboard may not match what you've entered.
I am sure there will be some technical bugs with strange cases, but I think I got the "happy paths" figured out. If you find something, please let me know.
Once I started working on this, it became apparent why I stuck with the brute force "Start Over"...
So, have fun..