The add-reference check is currently only shown pre-save.
Our main reason for not showing it mid-edit originally was that we felt it’d be noisy, since it’d be appearing when the user very-plausibly was still intending to add a reference and just hadn’t finished writing yet. But now we have access to a signal that basically means “I have moved on from this paragraph”, in the form of the branchNodeChange listener that we added for tone check.
In the suggestion mode patch for T399612 I pulled add-reference into mid-edit only for suggestions.
Particularly as we're about to be adding tone and paste as mid-edit checks, this seems like something useful to fill out the ranks.