The Flow panel holder supports the properties required to enable a progressive view. Use a Flow Panel holder for aligning fields on a form. You can also group the fields to ensure correct alignment of fields on a form. This panel offers functionality similar to the Collapsible (stacked). However, it does not have a panel header, and supports Container panel holder (Default), Sub Panel holder, and Section Panel holder types.
The following video (4:52) demonstrates creating Fixed panels in Developer Studio when you enable progressive views for a form: