Adornment grids allow an optional gridded framework to be drawn into an adornment as background markup to any notes being arranged atop the adornment.
The number of cells in the gird are controlled via $GridRows and $GridColumns. The cells can each be given a label via $GridLabels, which are drawn in $GridLabelFont at $GridLabelSize. The overall grid and labels are drawn in $GridColor and with $GridOpacity.
All these adjustments can be accessed via the Grid Properties pop-over which is accessed by the grid icon on any currently selected adornment.
The image shows a 2 row, 2 column grid with labelled cells; all other settings are default.
The use of a gird does not affect the OnAdd action of the adornment, which applies to a note regardless of where on the grid it is placed.