Board Thread:Support Requests - Designing Your Wiki/@comment-38643261-20200409013646/@comment-12913802-20200409035317

Since 2020.03.12, all new wikis created are part of the Unified Community Platform. Yours is one of these new communities and, at the moment, it's not possible to create custom CSS and JS in these wikis. But don't worry, it will be available again in the future!

"Many of you noticed that robust customization is not yet available on the Unified Community Platform. That is not a bug, that is intentional. Custom JS relies upon a content review system which is not yet ported from the legacy platform, so it will not be enabled until that happens. Having the simple customization options available now allows us to have a better baseline for chasing down core functionality bugs without issues being confounded by community customizations. Once we have the platform in a good place with core stability, we can let you get back to your usual creative ways :)"

- MisterWoodhouse on Thread:1828522

In other words, all you have to do is just wait until it gets released!

Tobias Alcaraz 03:53, April 9, 2020 (UTC)