Hi-
I think it might be as easy as running two consecutive commands:
First:
Delete /xpath=/my:myFields/my:group/my:repeatinggroup
then:
Insert /parent=/my:myFields/my:group /child=my:repeatinggroup
This will clear the ENTIRE repeating table, so any data that was typed before would be lost.
Let us know whether this works or whether something else is needed. Thanks!