This change is similar to D8424, for the "Icons" tab of the dialogue. In the current layout:
the controls are all of varying sizes and are not aligned, and the group titles are indented so far that they are not immediately recognisable as such.
The revised layout:
uses a single grid layout to enforce the sizes and alignment of the GUI controls.
Note that the screen shots above have had the QML tweaked to show all of the controls, in order to demonstrate the entire layout. In practice (and in the diff here of course) not all of the controls are shown depending on the containment type of the folder view.