We don't have a built in editor in TC except for vi.
So, the design was to use your favorite editor extension and create a small script.
This way you can also thoroughly test said script.
Then call the add2bootlocal.sh script to add your script to run.
Also this is a holdover from my work at DSL, where many GUI created scripts.
Then the GUI add2xxxxx could be used to add a call to the newly created script.