How to merge merged lines in mass addition

HI

We can not Merge two invoice lines which are created by merging its multiple lines.

Create two Invoices with Tax, Run Create Mass Addition. For each Invoice Two mass addition line generate one in status of MERGE and another NEW.

Now we can not merge both NEW status lines.

We have to first un-merge both the invoices and then merge all the lines. Is there any solution available.

thanks