Board Thread:Support Requests - Getting Technical/@comment-38811089-20200816071018/@comment-45117243-20200816095148

I'm not sure that you are supposed to be able to do so.

Where is the JS code from?

Basically, custom wiki JS code will work only after review and approval of FANDOM staff, after you request enabling JS review on your wiki. That does not include importing scripts from the dev wiki using ImportJS. For more information: Help:CSS and JS customization