Reasoning: In the original dialog the outline was merely a navigation tool. It was entirely optional. All interactions happened on the right side of the dialog, including adding parameters.
The new design is unusable without the outline because of the checkboxes. Without the outline we can't add parameters that aren't already there.
This is true in all situations, even in the single-template mode used by the Cite extension.
As a result it might be possible to merge the two dialog classes again. But this is outside of the scope of this ticket here.
Note this is purely a tech task. Nothing to demo here, except checking that the citation dialog still works.