Vertical Group Attribute

VerticalGroup is used to gather properties together in a vertical group in the inspector. This doesn't do much in and of itself, but in combination with other groups, such as HorizontalGroup attribute it can be very useful.
Vertical Group Multiple Stacked Boxes 

[HorizontalGroup("Split")]
[VerticalGroup("Split/Left")]
public InfoMessageType First;

[VerticalGroup("Split/Left")]
public InfoMessageType Second;

[HideLabel]
[VerticalGroup("Split/Right")]
public int A;

[HideLabel]
[VerticalGroup("Split/Right")]
public int B;


[TitleGroup("Multiple Stacked Boxes")]
[HorizontalGroup("Multiple Stacked Boxes/Split")]
[VerticalGroup("Multiple Stacked Boxes/Split/Left")]
[BoxGroup("Multiple Stacked Boxes/Split/Left/Box A")]
public int BoxA;

[BoxGroup("Multiple Stacked Boxes/Split/Left/Box B")]
public int BoxB;

[VerticalGroup("Multiple Stacked Boxes/Split/Right")]
[BoxGroup("Multiple Stacked Boxes/Split/Right/Box C")]
public int BoxC, BoxD, BoxE;