Creating new page with Javascript code

There are a number of code snippet plugins. Some may be PHP focused only, but maybe there are some that support JS.
https://ww.wp.xz.cn/plugins/search/code+snippet/

TBH, getting JS code in an external file(s) loaded for a particular page isn’t all that complicated. A few lines of PHP code which could be added to your theme’s functions.php or a very simple custom plugin.

External JS files are enqueued with wp_enqueue_script(), called from a callback hooked to “wp_enqueue_scripts” action. Conditionally enqueue based on get_queried_object_id() returned value to target one specific page.
https://developer.ww.wp.xz.cn/reference/functions/wp_enqueue_script/