public AllowMergingEnum AllowMergingFixed {get; set;}
'Declaration
Public Property AllowMergingFixed As AllowMergingEnum
By default, this property is set to AllowMergingEnum.Default, which causes fixed cells to be merged with the same setting as scrollable cells.
If you specify a different value for this property, you can use different merging modes for fixed cells such as column headers than the setting used for scrollable cells.