After migration to UCP, the UI for the extension CharInsert is no longer available in the VisualEditor, not even in "VisualEditor - source mode". Unfortunately, this makes inserting references and templates on the wiki harder, requiring users to type out or copy-paste the ref tag and the template wikitext. Before migration this was a single click.
If I could, I would just replicate the same functionality in the VisualEditor, but this is not possible either. See my previous post: https://community.fandom.com/f/p/4400000000001905690
Side note: CharInsert is available in "Source editor", but this is not the default setting. Which means that 99.9% of users won't be able to use it, making it useless. And even then, it is now placed below the editor and below the "Save changes" button, which makes it less convenient than before migration to UCP.