Cells Merged in a Longitudinal Direction

Now, the most conscious of problem I have is about to duplicate some rows of a table in the InDesign’s document. The rows have some cells merged in a longitudinal direction. I want to duplicate them with the cells merged, so I tried a command “duplicate” as an argument that was a reference of a range of the rows. But the command wasn’t working to duplicate the rows all together. I was sure that, for adding rows, it seems that I have to make some new rows and copy every content and property of the original rows into the new rows. But the how using “make” and “copy” is very very slow. It is not so hot. Is there anything other way else?