The ZC157 version of admin javascript loader will pull in files per page.
as described in detail here:
https://docs.zen-cart.com/dev/admin/templating/

This ceon javascript is required on two pages: product and categories.
So, you could put the ceon code in two files named as product.php and categories.php in the /javscript folder, and they would be pulled into the head of the corresponding pages.
But since there is already a core product.php in use, and I want to maintain that as is, you can use a separate product_whatever.php file, and that will be pulled in too.
And, to only have one CEON javascript code block, and make it obvious it exists, I leave it named as such in /javascript but be called by both product_whatever.php and categories.

So, three new files, that will be obvious for upgrades, and no core files harmed, all in /javascript.

And for those wondering what all this is about, this ceon javascript is what adds the Uri mapping fields on the end of those pages, without modifying those pages.