As mentioned, Map Viewer Classic (and the Visualization tab, when still formatted in the same way as Map Viewer Classic) used to allow you to reorder your fields.
When you update pop-ups in New Map Viewer, it orders your fields alphabetically rather than in the order it was published, which according to some forum posts seems to be intentional, but does not make sense as the community has expressed.
Now, because the "Save Layer" option in Map Viewer Classic has been removed, New Map Viewer does not seem to allow you to reorder your fields for your maps and in the table (in the Data tab), unless I am mistaken.
