Block Themes, like Twenty Twenty-Three, don’t use the Customizer, which is where you would have found the Additional CSS setting.
It’s recommended that you make any changes you would have used CSS for directly to the blocks instead: https://ww.wp.xz.cn/documentation/article/site-editor/
There’s also a video tutorial if you prefer that style: https://learn.ww.wp.xz.cn/tutorial/intro-to-the-site-editor-and-template-editor/
With that said, you can still access the Customizer via /wp-admin/customize.php and, at least for now, Additional CSS there will still work on the whole theme.
I also want to know what happened to all the CSS I had in the old one. A lot of that was carried over from prior versions of the site with common CSS tags that I use frequently. So I want to know what happened to it because I’ve been on Twenty-Twenty-Three for over a year and it only just now disappeared. Further, the other site, using the exact same theme has that Additional CSS item in the menu, so it doesn’t make the least bit of sense that it’s gone.
Additional CSS is attached to the theme you’re using.
If you change themes at any point, you will lose the content. If you didn’t change themes, then the content will still be there under /wp-admin/customize.php
I have not changed themes and the CSS is not there at all. That is exactly my problem.
Are you saying that Additional CSS under /wp-admin/customize.php is empty, or that you can’t find Additional CSS under /wp-admin/customize.php?
The “work around” link you provided is blank.
But I still don’t understand how, without changing anything, that Additional CSS menu item disappeared and why, using the exact same theme on another site still has the Additional CSS menu item.
So, really, I have two issues.
