What inserting it does: 'control' puts the control on the cells and keeps their values;
'richData' writes the kind's default value into them.
The entry's icon, or null.
The sdk kind's label, or the type when the kind has none.
The control type or the rich data type, as registered in the SDK.
A type of cell content that a UI can offer to insert: a cell control or a rich data value.