permanize changes to panel.js?

[Toller Kerl]

I've edited panel.js to add the ability to invoke the System Monitor from the menu displayed on r/c of the center panel, per the direction given in viewtopic.php?t=371791 (and thanks very much for that, @mantom).

However, every time there's an update of Cinnamon -- seemingly weekly -- the change is lost and I have to redo it. Meld makes this quite a bit easier, but is there another, better way to make such a customization more permanent? If it was C++ I'd include the code in header files and insert them via #include directives, but it's JavaScript and I don't know of a similar construct.

Any and all help appreciated!