I really like how you can configure the forms in Field Maps with attribute groups and conditional visibility. I would love to see this functionality available in the basic popups for web maps and Field Maps, not just in the editing dialog. The new web map viewer allows you to control the order of fields easily, which is a step in the right direction, but grouping would be incredibly helpful.
This functionality would give map designers much more flexibility in how information is displayed to end users in the office and in the field.