It should be able to do what the input and stage keyline cards in aggregation does:

• expand/collapse
• left area for text and controls (starting next to expand/collapse)
• right area for text and controls
• standardised spacing
• for now (unlike the design) keep the stage-specific help text and stick it in the right controls before the buttons

The reasoning is that the input area and stage already ran out of sync. We need to change the stage's header which is currently two separate controls (editor toolbar and preview toolbar) into one and then only the editor and preview below is resizable. ie the resize control/line shouldn't cut over the header like it currently does.