AFAIK, under "My Rigs" you will find the rigs that have your own name in the field "Author". My guess is that if you take a rig that was not created by you and modify the "Author" tag to fill in your own KPA name, then that rig should appear under "My Rigs".
PS: Pressing and holding the Rig button makes the rig appear/disappear in "Favourites" (not in "My Rigs").