Thank you for reaching out again with your
query.
Unfortunately, the specific functionality you
are requesting hiding lower-level rows when a group has only one item, clicking
on a second-level row to retrieve third-level key values, and selectively
collapsing group level is not feasible.
Additionally,
using a DetailTemplate for these capabilities is currently unsupported. The
DetailTemplate feature is designed to add custom detail layouts for rows, but
it does not allow modifying grouping behavior or controlling the visibility of
groups based on item count conditions. Thanks for the your understanding.