Please check the attached sample project.
ConsoleApp27.zip (218.8 KB)
You need to restore the Nuget package of Aspose.Cells, I’m using version 188.8.131.52.
The Excel template is named GroupMergeWithHorizontal.xlsx, there is only one cell with Smart Marker:
I have attached a screenshot of the result, which the cells with same value “A” are not merged.
And there is another issue I found, if the cells with smart markers are merged in the template, when the smart markers contains “shift”, the generated rows are not with the same style (border in my sample). Please check the Excel template “ShiftWithMergedCells.xlsx”, and the screenshot of result “Wrong_Result_of_ShiftWithMergedCells.JPG”.