[Actually deletes the previous entry. This was based on a bad guess.]
I would like to paste a new group where necessary, and then delete the cells and columns so that they match the numbers for the two groups that correspond to the number: then you can copy and paste the cells (many at once) from the old group to the new one.
Make sure your grouping formulas or fields match, and then delete the old group.
(You may have already discovered this, but a simple way to create groups is to drag and drop fields from the "Report data" into the "Row group" twist: this method will refuse to create a group below the details.)
I think the only alternative is to edit XML, and this is dangerous: be careful and install older versions if necessary.
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